📚 Year 12 WJEC Biology: Key Points for Experimental/Practical Assessments | Year 12 WJEC 生物：实验/实践考核要点
Practical work is at the heart of the WJEC Year 12 Biology specification. It not only reinforces theoretical concepts but also develops the investigative and analytical skills that are essential for success in both written examinations and the Practical Endorsement. This article covers the key practical skills, common experiments, data-handling techniques, and safety considerations you need to master for your assessments.
实践操作是 WJEC 高一生物课程的核心。它不仅巩固理论知识，还培养研究与分析技能，这些技能对于笔试和实践认证的成功至关重要。本文涵盖了您需要掌握的关键实践技能、常见实验、数据处理技术以及安全注意事项。
1. Mastering the Light Microscope and Calibration | 掌握光学显微镜与校准
The light microscope is fundamental to many practicals, from observing cells to identifying stages of mitosis. You must be able to set up the microscope correctly, starting with the lowest power objective and adjusting the condenser and iris diaphragm to optimise illumination. Always use the coarse focus first, then the fine focus, and never use the coarse focus with high-power objectives to avoid damaging the slide.
光学显微镜是许多实验的基础，从观察细胞到识别有丝分裂阶段都离不开它。你必须能够正确设置显微镜，从最低倍物镜开始，调整聚光镜和虹彩光圈以获得最佳照明。始终先使用粗调焦，再用细调焦，并且切勿在高倍物镜下使用粗调焦，以免损坏玻片。
r for each objective lens. Record how many graticule divisions correspond to a known number of micrometre divisions, then calculate the length represented by one eyepiece unit. For example, if 10 graticule units align with 0.1 mm (100 µm) on the stage micrometer, then 1 eyepiece unit = 10 µm. Always show your working clearly.
目镜测微尺的校准是一项必备技能。由于测微尺刻度是任意的，必须针对每个物镜用镜台测微尺进行校准。记录多少格目镜刻度对应已知的镜台微米刻度，然后计算一个目镜单位代表的长度。例如，如果10个目镜单位与镜台上的0.1毫米（100微米）对齐，那么1个目镜单位=10微米。务必清晰展示计算过程。
proportional and labelled with a title and magnification. Include a scale bar rather than stating '×400', as the former is independent of reproduction size.
在根据显微镜下的影像绘制生物标本时，请使用削尖的铅笔，绘制清晰连续的线条，不要使用阴影。绘图应比例适当，并附上标题和放大倍数。最好使用比例尺，而不是写“×400”，因为比例尺不受复制尺寸的影响。
2. Biochemical Tests for Biological Molecules | 生物分子的生化检测
g and non-reducing sugars, starch, proteins, and lipids. For reducing sugars, add Benedict' ick-red precipitate, depending on the concentration. Always use a control of distilled water.
你必须了解针对还原糖与非还原糖、淀粉、蛋白质和脂质的特定检测方法。对于还原糖，向样品中加入等体积的本尼迪克特试剂，并在约80°C的水浴中加热。阳性结果为颜色从蓝色→绿色→黄色→橙色→砖红色沉淀的变化，具体取决于浓度。始终设置蒸馏水作为对照。
To test for non-reducing sugars like sucrose, first hydrolyse with dilute hydrochloric acid and heat, then neutralise with sodium hydrogencarbonate before adding Benedict's reagent. The hydrolysis breaks the glycosidic bond, releasing reducing sugars. Starch is tested by adding a few drops of iodine in potassium iodide solution; a blue-black colour indicates starch. The test must be performed at room temperature—heating will break the starch-iodine complex and cause the colour to fade.
要检测蔗糖等非还原糖，首先用稀盐酸水解并加热，然后用碳酸氢钠中和，最后加入本尼迪克特试剂。水解作用会打断糖苷键，释放出还原糖。检测淀粉时滴加几滴碘-碘化钾溶液；蓝黑色表示存在淀粉。该检测必须在室温下进行——加热会破坏淀粉-碘复合物，导致颜色褪去。
Proteins are detected with the biuret test: add sodium hydroxide solution, then a few drops of dilute copper(II) sulfate solution. A purple colour indicates peptide bonds. For lipids, the emulsion test involves dissolving the sample in ethanol and then pouring into cold water; a milky-white emulsion confirms the presence of lipids. Always wear eye protection when using ethanol and sodium hydroxide.
蛋白质通过双缩脲试验检测：先加入氢氧化钠溶液，然后滴加几滴稀硫酸铜溶液。紫色表示存在肽键。对于脂质，乳化试验包括将样品溶于乙醇，然后倒入冷水中；乳白色乳浊液确认存在脂质。使用乙醇和氢氧化钠时务必佩戴护目镜。
3. Enzyme Activity and Factors Affecting Rate | 酶活性及其影响因素
Experiments on enzyme activity often use catalase (from potato or liver) breaking down hydrogen peroxide into water and oxygen, or amylase digesting starch. You need to be able to measure the rate of reaction by recording the volume of oxygen produced over time, or by timed sampling with iodine solution. A water bath is essential to control temperature, while buffer solutions maintain a constant pH.
酶活性实验常使用过氧化氢酶（来自马铃薯或肝脏）将过氧化氢分解为水和氧气，或使用淀粉酶消化淀粉。你需要能够通过记录随时间产生的氧气体积，或通过碘液定时取样来测量反应速率。水浴对于控制温度至关重要，而缓冲溶液则用于维持恒定的pH值。
When investigating the effect of temperature, allow the enzyme and substrate solutions to equilibrate in the water bath separately for at least 5 minutes before mixing. This ensures that the reaction starts at the desired temperature. Plot a graph of rate (y-axis) against temperature (x-axis). The rate initially increases due to increased kinetic energy and more frequent successful collisions, but after the optimum, the rate declines sharply as the enzyme denatures and the active site loses its complementary shape.
研究温度影响时，先将酶和底物溶液分别在水浴中平衡至少5分钟，然后再混合。这确保反应在所需温度下开始。绘制速率（y轴）对温度（x轴）的曲线图。速率起初因动能增加和成功碰撞更频繁而上升，但超过最适温度后，速率急剧下降，因为酶变性，活性位点失去了互补形状。
For pH experiments, use buffer solutions from pH 2 to pH 10 and repeat the procedure. Remember that pH affects the charges on the amino acid side chains, altering ionic and hydrogen bonds that maintain the tertiary structure. Extreme pH can denature the enzyme irreversibly. Always use a fresh sample of enzyme for each pH to avoid cross-contamination. When calculating initial rate, use the tangent to the progress curve at time zero.
进行pH值实验时，使用pH 2至pH 10的缓冲溶液，并重复实验步骤。记住，pH值会影响氨基酸侧链上的电荷，改变维持三级结构的离子键和氢键。极端pH值可能使酶发生不可逆变性。每个pH值都应使用新鲜酶样，避免交叉污染。计算初始速率时，使用反应进程曲线在时间零点处的切线。
4. Osmosis and Water Potential in Plant Tissues | 植物组织中的渗透作用与水势
h is measured after a fixed period (e.g., 30 minutes). Blot the cylinders gently before weighing to remove surface water— tting technique is vital for reliability. Calculate percentage change in mass: (final mass – initial mass) / initial mass × 100.
要研究渗透作用，你可以使用马铃薯圆柱体或洋葱表皮，置于一系列不同浓度的蔗糖或盐溶液中。在固定时间（例如30分钟）后测量质量或长度的变化。称重前轻轻吸干圆柱体表面的水分——一致的吸水技巧对数据可靠性至关重要。计算质量变化百分比：(最终质量 – 初始质量) / 初始质量 × 100。
Plot a graph of percentage change in mass against concentration. The point where the curve crosses the x-axis (zero change) represents the approximate water potential of the tissue. Explain that water moves by osmosis from a region of higher water potential (less negative) to a region of lower water potential (more negative). In a hypotonic solution, the plant cells become turgid; in a hypertonic solution, they become plasmolysed.
绘制质量变化百分比对浓度的曲线图。曲线与x轴的交点（零变化）代表组织的大致水势。解释水分子通过渗透作用从水势较高（负值较小）的区域向水势较低（负值较大）的区域移动。在低渗溶液中，植物细胞变得硬挺；在高渗溶液中，它们发生质壁分离。
When observing plasmolysis under the microscope, use a strip of onion epidermis mounted in a drop of water, then draw through a concentrated sucrose or salt solution using filter paper. The cell membrane pulls away from the cell wall as water leaves the vacuole. Plasmolysis is reversible (deplasmolysis) if the cells are not left in the hypertonic solution too long. Always use a coverslip and handle sharp scalpel blades with care.
在显微镜下观察质壁分离时，取一条洋葱表皮置于水滴中，然后用滤纸吸过浓蔗糖或盐溶液。随着水分离开液泡，细胞膜会从细胞壁上脱落下来。如果细胞在高渗溶液中放置时间不长，质壁分离是可逆的（质壁分离复原）。务必使用盖玻片，并小心处理锋利的刀片。
5. Photosynthesis and the Starch Test on Leaves | 光合作用与叶片淀粉检测
The classic experiment uses a variegated leaf (e.g., geranium) or a leaf partially covered with black paper to test whether chlorophyll and light are necessary for starch production. After the plant has been destarched by placing it in the dark for 24–48 hours, expose the leaf to bright light for several hours. Then, kill the leaf by immersing in boiling water to stop metabolic reactions.
经典实验使用斑叶（例如天竺葵）或用黑纸部分遮盖的叶片，来检验叶绿素和光照是否为合成淀粉所必需。将植株在黑暗中放置24–48小时耗尽淀粉后，将叶片置于强光下数小时。然后，将叶片放入沸水中煮沸，以终止代谢反应。
Next, decolourise the leaf by boiling it in ethanol in a water bath (never heat ethanol directly with a Bunsen burner due to its flammability). The ethanol extracts chlorophyll, making the leaf pale. Then, soften the leaf in warm water and spread it on a white tile. Add iodine solution. The areas that received light and contain chlorophyll will turn blue-black, while the white parts of the variegated leaf and the covered areas will remain pale or iodine-coloured.
接下来，将叶片在热水浴中的乙醇里煮沸使其脱色（由于乙醇易燃，切勿用本生灯直接加热）。乙醇提取出叶绿素，使叶片变得苍白。然后将叶片在温水中软化，铺在白瓷板上。滴加碘液。接受光照并含有叶绿素的区域会变成蓝黑色，而斑叶的白色部分和被遮盖区域则保持淡色或碘液颜色。
You must be able to explain the safety precautions: using a water bath for ethanol, wearing eye protection, and using forceps to handle the hot leaf. Also, explain why destarching is needed: to remove any pre-existing starch that would confound the results. Control variables include CO₂ concentration, temperature, and the plant species used.
你必须能够解释安全预防措施：使用水浴加热乙醇，佩戴护目镜，用镊子夹取烫手的叶片。此外，解释为何需要耗竭淀粉：去除任何预先存在的淀粉，以防干扰实验结果。控制变量包括二氧化碳浓度、温度以及所用的植物种类。
6. Measuring the Rate of Respiration Using a Respirometer | 使用呼吸计测量呼吸速率
A respirometer measures oxygen consumption by organisms such as germinating peas or maggots. The apparatus consists of a sealed chamber connected to a manometer (U-tube with coloured liquid). As the organism respires aerobically, it absorbs oxygen, and any CO₂ produced is absorbed by a chemical such as soda lime or potassium hydroxide solution. The decrease in gas volume causes the manometer liquid to move towards the chamber.
呼吸计用于测量发芽豌豆或蝇蛆等生物体的耗氧量。该装置由一个连接到压力计（装有有色液体的U型管）的密封室组成。当生物体进行有氧呼吸时，会吸收氧气，而产生的二氧化碳则被碱石灰或氢氧化钾溶液等化学物质吸收。气体体积的减少导致压力计液柱向小室方向移动。
To calculate the rate of oxygen consumption, record the distance moved by the liquid over a known time period. Multiply this distance by the cross-sectional area of the capillary tube to obtain the volume of oxygen used. Express the rate as volume per unit time per unit mass of organism (e.g., mm³ min⁻¹ g⁻¹). A control tube with glass beads of equal mass corrects for changes in atmospheric pressure and temperature.
要计算耗氧速率，记录液柱在已知时间内移动的距离。将此距离乘以毛细管的横截面积，得到消耗的氧气体积。速率表示为每单位质量生物体在单位时间内的体积变化（例如 mm³ min⁻¹ g⁻¹）。使用相同质量的玻璃珠作为对照管，以校正大气压力和温度变化的影响。
Common sources of error include leaks, incomplete CO₂ absorption, and temperature fluctuations. Ensure all connections are airtight, use fresh soda lime, and allow the apparatus to equilibrate for 10-15 minutes before starting measurements. Also, avoid direct sunlight on the apparatus to prevent temperature increases that would expand gases.
常见的误差来源包括漏气、二氧化碳吸收不完全以及温度波动。请确保所有连接处气密，使用新鲜的碱石灰，并在开始测量前让装置平衡10-15分钟。此外，避免阳光直射装置，以防温度升高导致气体膨胀。
7. Investigating Transpiration with a Potometer | 用蒸腾计研究蒸腾作用
A potometer measures the rate of water uptake by a leafy shoot, which is assumed to be equivalent to the transpiration rate under constant conditions. Cut the shoot under water to prevent air locks in the xylem, and insert it into the potometer under water. The apparatus is filled with water, and an air bubble is introduced into the capillary tube. Measure the distance the bubble moves in a given time.
蒸腾计用于测量带叶枝条的吸水速率，在恒定条件下可认为大致等于蒸腾速率。在水下剪切枝条，以防止木质部出现气栓，并在水下将其插入蒸腾计。装置充满水，向毛细管中引入一个气泡。测量气泡在给定时间内移动的距离。
Variables you can investigate include light intensity (using a lamp at different distances), wind speed (using a fan), humidity (using a plastic bag or spraying water), and temperature. Only change one factor at a time while keeping others constant. Plot the rate of water uptake against the independent variable. Explain that transpiration is driven by the water potential gradient from the leaf to the atmosphere, and that stomatal opening is influenced by guard cell turgor.
你可以研究的变量包括光照强度（使用不同距离的灯）、风速（使用风扇）、湿度（使用塑料袋或喷水）和温度。一次只改变一个因素，保持其他因素不变。绘制吸水速率对自变量的曲线图。解释蒸腾作用由叶片到大气的水势梯度驱动，并且气孔开闭受保卫细胞膨压的影响。
A common mistake is to measure transpiration rate directly with a potometer; in reality, a small amount of the water taken up is used in photosynthesis and for cell turgidity, but it is a very close approximation. Also, always return the bubble by opening the reservoir tap before it reaches the end of the scale. Wear gloves when handling plant sap as some plants produce irritants.
常见的错误是认为蒸腾计直接测量蒸腾速率；实际上，吸收的水分中有一小部分用于光合作用和维持细胞膨压，但这是一个极其接近的近似值。另外，在气泡到达刻度末端之前，务必打开储液器旋塞使气泡复位。处理植物汁液时需戴手套，因为某些植物会产生刺激性物质。
8. Data Recording, Tables, and Graph Skills | 数据记录、表格和图表技能
In practical assessments, you are frequently evaluated on your ability to present data clearly. Tables should have clear ruled lines, headings with units (e.g., 'Temperature / °C'), and the independent variable in the first column. Do not put units in the body of the table. Record raw data to the precision of the measuring instrument, and use a consistent number of decimal places.
在实践考核中，经常评估你清晰呈现数据的能力。表格应有清晰的边框，标题需带单位（例如“温度 / °C”），自变量放在第一列。不要在表格主体内写单位。记录原始数据时应反映测量仪器的精度，并保持小数点位数一致。
se a sharp pencil. Plot points as small crosses (×) or encircled dots. A line of best fit should be smooth and balanced with equal numbers of points on either side; it need not pass through every point, especially when experimental error is present. For rate determination, know how to draw a tangent to a curve and calculate its slope: (change in y) / (change in x).
绘制图表时，选择合适的刻度，使坐标轴上的网格至少利用一半。坐标轴需标注物理量和单位，并使用削尖的铅笔。数据点以小十字（×）或带圈圆点标出。最佳拟合线应平滑、平衡，两侧点数大致相等；它不一定通过所有点，尤其在存在实验误差的情况下。测定速率时，应知道如何作曲线的切线并计算其斜率：(y的变化量) / (x的变化量)。
Always describe the trend in data clearly: use phrases like 'as X increases, Y increases/decreases until…' or 'there is a positive correlation'. If the graph shows an optimum, identify it with a specific value. Anomalous points should be identified and excluded from the line of best fit, with a brief justification (e.g., 'reading error' or 'temperature fluctuation').
始终清晰地描述数据趋势：使用诸如“随着X增加，Y增加/减少直到……”或“存在正相关”等说法。若图表出现最适点，应指明其具体数值。识别异常点，并在最佳拟合线中排除，同时附上简要理由（例如“读数错误”或“温度波动”）。
9. Statistical Tests: Chi-Squared and Student's t-test | 统计检验：卡方检验与t检验
to compare observed frequencies with expected frequencies. For example, a genetic cross predicting a 3:1 phenotype ratio. The formula is χ² = Σ[(O – u must be able to state the null hypothesis, calculate χ², determine degrees of freedom (n – are with a critical value at p = 0.05. If χ² > critical value, reject the null hypothesis.
WJEC 考纲要求你理解两种统计检验的应用。卡方（χ²）检验用于类别数据，将观察频数与期望频数进行比较。例如，预测表型比为3:1的遗传杂交。公式为 χ² = Σ[(O – E)² / E]。你必须能够陈述零假设，计算 χ² 值，确定自由度（n – 1），并与 p=0.05 下的临界值比较。若 χ² > 临界值，则拒绝零假设。
Student's t-test compares the means of two normally distributed datasets to see if they are significantly different from each other. There are two types: paired t-test (for repeated measures) and unpaired t-test (for two independent samples). For the unpaired t-test, you first calculate the mean and standard deviation of each set. The formula is:
t检验用于比较两个正态分布数据集的均值，看它们是否彼此存在显著差异。有两种类型：配对t检验（用于重复测量）和非配对t检验（用于两个独立样本）。对于非配对t检验，首先计算每组的均值和标准差。公式如下：
t = (x̄₁ – x̄₂) / √[ (s₁²/n₁) + (s₂²/n₂) ]
You then determine degrees of freedom (typically n₁ + n₂ – 2) and look up the critical t-value. If the calculated t exceeds the critical value, the null hypothesis (that there is no significant difference between the means) can be rejected. Always interpret the conclusion in the context of the experiment.
然后确定自由度（通常为 n₁ + n₂ – 2），并查表得出临界t值。若计算出的 t 值超过临界值，则可拒绝零假设（即两均值间无显著差异）。务必结合实验背景解释结论。
10. Risk Assessment and Ethical Considerations | 风险评估与伦理考量
res. Common hazards in biology practicals include: hot liquids (Bunsen burner, water bath), sharp instruments (scalpel, dissection scissors), corrosive chemicals (sodium hydroxide, biuret reagent, concentrated acids), biological materials (bacteria cultures), and allergens (enzymes, pollen).
每项实践活动都需要进行风险评估。你必须识别危险，评估风险（可能性×严重程度），并说明控制措施。生物实验中的常见危险包括：热液体（本生灯、水浴）、锐器（解剖刀、解剖剪）、腐蚀性化学品（氢氧化钠、双缩脲试剂、浓酸）、生物材料（细菌培养物）以及过敏原（酶、花粉）。
Control measures include wearing eye protection, using water baths instead of direct heating for ethanol, wiping up spills immediately, using aseptic technique when handling microorganisms, and disposing of biological waste correctly (autoclaving before disposal). Always tie back long hair and remove dangling jewellery when using a Bunsen burner.
控制措施包括佩戴护目镜、使用水浴而非直接加热乙醇、立即擦拭溢出物、处理微生物时采用无菌技术，以及正确处置生物废弃物（废弃前高压灭菌）。使用本生灯时，务必扎起长发并摘除下垂的饰品。
Ethical considerations are particularly important when using living organisms. Replace animals with plant tissues or microbial models where possible (the three Rs: Replacement, Reduction, Refinement). If animals must be used, minimise distress, handle them gently, and return them to their habitat promptly. Always consider the ethical implications of genetic modification experiments and ecological investigations that may disturb habitats.
使用活体生物时，伦理考量尤为重要。尽可能用植物组织或微生物模型替代动物（3R原则：替代、减少、优化）。若必须使用动物，应尽量减少其痛苦，轻拿轻放，并尽快将其送回栖息地。始终考虑转基因实验以及可能干扰栖息地的生态调查所带来的伦理影响。
11. Serial Dilutions and Standard Curves | 系列稀释与标准曲线
Making serial dilutions is a routine skill in biochemistry and microbiology. Starting from a stock solution of known concentration (e.g., 1% starch or 0.1 M glucose), you can create a series of concentrations by transferring a fixed volume (e.g., 1 cm³) into a known volume of distilled water (e.g., 9 cm³) to make a 1 in 10 dilution, then repeating. Label each tube clearly with the concentration and remember to use a clean pipette for each transfer to avoid carry-over.
制作系列稀释液是生物化学和微生物学中的常规技能。从已知浓度的储备液（例如1%淀粉溶液或0.1 M葡萄糖溶液）开始，通过将固定体积（如1 cm³）转移至已知体积的蒸馏水（如9 cm³）中，制成10倍稀释液，然后重复操作。清楚地标注每支试管的浓度，并记得每次转移使用干净的移液管，以避免交叉污染。
Standard curves are used to determine the concentration of an unknown sample. For example, after performing Benedict's test on a range of known glucose concentrations, you might filter and read the absorbance using a colorimeter, or use a comparison chart for colour intensity. Plot absorbance (y-axis) against concentration (x-axis). The concentration of the unknown can be read directly from the graph. Alternatively, for enzyme kinetics, you may plot a calibration curve of product concentration against absorbance.
标准曲线用于测定未知样品的浓度。例如，在对一系列已知浓度的葡萄糖进行本尼迪克特检验后，你可以过滤溶液并用比色计读取吸光度，或使用比色卡比较颜色深浅。绘制吸光度（y轴）对浓度（x轴）的曲线图。未知样品的浓度可直接从图表中读出。或者，在研究酶动力学时，你可以绘制生成物浓度对吸光度的校准曲线。
When using a colorimeter, select the appropriate filter (often red for blue/green solutions, and green for red solutions) and zero the instrument with a blank (distilled water or the reagent without the substance being tested). The blank accounts for the absorbance of the solvent and cuvette. Always handle cuvettes by the frosted sides and wipe the clear sides before inserting into the colorimeter.
使用比色计时，选择合适的滤光片（蓝色/绿色溶液常用红色滤光片，红色溶液常用绿色滤光片），并利用空白（蒸馏水或不含待测物质的试剂）对仪器进行调零。空白可扣除溶剂和比色皿的吸光度。操作比色皿时，始终手持磨砂面，在插入比色计前擦拭透明面。
12. Common Pitfalls and How to Avoid Them | 常见陷阱及如何避免
A recurring issue in examinations is the failure to recognise control variables. When asked to design an experiment, explicitly list the variables you will control and how—e.g., using a water bath at 25 °C, adding equal volumes of enzyme, using the same batch of starch. Never say 'keep everything the same' without specifying what 'everything' includes.
考试中反复出现的一个问题是未能识别控制变量。当要求设计实验时，要明确列出你将要控制的变量及控制方法——例如，使用25°C恒温水浴，加入等体积酶液，使用同一批次的淀粉。不要说“保持一切不变”，而不具体说明“一切”包括哪些内容。
Another pitfall is poor justification of replicates. Repeating the experiment three times and calculating a mean improves reliability by reducing the effect of random errors. However, replicates do not compensate for systematic errors (e.g., a faulty thermometer). Always state that replicates identify anomalies and allow statistical analysis.
另一个陷阱是为重复实验提供的理由不充分。重复实验三次并计算平均值可减少随机误差的影响，从而提高可靠性。然而，重复实验并不能弥补系统误差（例如温度计故障）。始终要说明，重复实验可以识别异常值，并允许进行统计分析。
Finally, when answering questions on practical techniques, use precise biological vocabulary: 'denatured', 'control', 'reliability', 'accuracy', 'resolution', 'range', 'anomalous', 'correlation', 'calibration curve', 'asymptotic'. Marks are often lost for vague language. Review past-paper mark schemes to familiarise yourself with the expected terminology. Remember, WJEC papers frequently ask you to evaluate experimental design, so practice spotting flaws in given methods.
最后，在回答有关实验技术的问题时，请使用准确的生物学术语：“变性”、“对照”、“可靠性”、“准确度”、“分辨率”、“范围”、“异常”、“相关性”、“校准曲线”、“渐近的”。用语含糊经常会失分。复习往年试卷评分方案，熟悉所需术语。请记住，WJEC 试卷经常要求你评估实验设计，因此请练习找出给定方法中的缺陷。
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图