The component of soil which makes the air above the soil in a farmland shimmer on a hot summer day is :

Options

A. humus
B. air
C. water
D. sand

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about a component of soil that causes the air above farmland to shimmer on a hot summer day.

2. **Identifying the Components of Soil**: The main components of soil include humus, air, water, and sand. Each of these has different properties.

3. **Analyzing the Options**:
- **Humus**: This is the organic matter in soil, dark in color, and contributes to soil fertility but does not cause shimmering.
- **Air**: While air is present in soil, it does not shimmer.
- **Water**: Water can create reflections but is not a solid component of soil.
- **Sand**: Sand consists of fine particles that can reflect sunlight, creating a shimmering effect.

4. **Conclusion**: The component of soil that makes the air above farmland shimmer on a hot summer day is **sand**. When sunlight hits the fine particles of sand, it causes a sparkling or shimmering effect.

5. **Final Answer**: The correct answer is **sand**.

---