[A]: The downward· movement of minerals through soil is effected by quantity and pH of water.
[R]:. Water makes mineral ions available to roots. The lower the pH, greater the leaching power of water.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To analyze the statements provided in the question, we need to break down both the assertion [A] and the reason [R] and evaluate their validity.

### Step-by-Step Solution:

1. **Understanding the Assertion [A]:**
- The assertion states that the downward movement of minerals through soil is affected by the quantity and pH of water.
- This is true because the movement of minerals in soil is influenced by how much water is present (quantity) and its acidity or alkalinity (pH).

2. **Understanding the Reason [R]:**
- The reason states that water makes mineral ions available to roots and that lower pH increases the leaching power of water.
- This is also true. Water dissolves mineral ions, making them accessible for plant uptake. Additionally, lower pH (more acidic conditions) can enhance the leaching process, where minerals are washed away from the soil.

3. **Explaining the Relationship:**
- The assertion and reason are connected. The quantity of water affects how minerals move through soil, and the pH of the water influences the availability of these minerals to plants.
- Higher water quantity can lead to leaching, while lower pH can increase the solubility of certain minerals, making them more available to plants.

4. **Conclusion:**
- Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the answer is that both statements are true, and the reason is a valid explanation for the assertion.

### Final Answer:
Both [A] and [R] are true, and [R] is the correct explanation for [A].

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