The most important external factor for seed germination is

Options

A. Light
B. Soil
C. Oxygen
D. Water

Answer

**Step-by-Step Solution:**

1. **Understanding Seed Germination**: Seed germination is the process by which a seed develops into a new plant. For this process to occur, certain external factors are crucial.

2. **Identifying External Factors**: The main external factors that influence seed germination include:
- Type of soil
- Availability of water
- Concentration of oxygen
- Presence of light

3. **Analyzing the Importance of Water**: Among these factors, water is essential for germination. Seeds contain stored food that is in a dry form, which cannot be utilized by the developing embryo without water.

4. **Role of Water in Germination**: Water helps in dissolving the stored food, allowing the embryo to absorb it. Without water, the food remains inaccessible to the seed.

5. **Oxygen Requirement**: Seeds also require oxygen for respiration. However, they can only utilize dissolved oxygen in water. If there is too much water, it can lead to a lack of oxygen, which can inhibit germination.

6. **Conclusion**: Given the analysis of the factors, water is the most critical external factor for seed germination, as it is necessary for both the utilization of stored food and the absorption of oxygen.

**Final Answer**: The most important external factor for seed germination is **water**.

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