What is not true about air?

Options

A. It makes the windmill rotate.
B. It helps in the movements of aeroplanes.
C. Birds can fly due to presence of air.
D. It has no role in water cycle

Answer

To determine what is not true about air, we will analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Evaluate the First Statement**:
- **Statement**: "It makes the windmill rotate."
- **Analysis**: This statement is true. Air is essential for windmills as it provides the wind that causes the blades to rotate, which can be used for generating electricity or grinding grains.

2. **Evaluate the Second Statement**:
- **Statement**: "It helps the movement of aeroplanes."
- **Analysis**: This statement is also true. Air provides the necessary lift and thrust for airplanes to fly, making it crucial for their movement.

3. **Evaluate the Third Statement**:
- **Statement**: "Birds can fly due to the presence of air."
- **Analysis**: This statement is true as well. Birds rely on air for lift and to navigate while flying.

4. **Evaluate the Fourth Statement**:
- **Statement**: "It has no role in the water cycle."
- **Analysis**: This statement is not true. Air plays a significant role in the water cycle, particularly in processes like evaporation and condensation. Water evaporates into vapor in the presence of air, and when it cools, it condenses to form clouds.

### Conclusion:
The statement that is not true about air is: **"It has no role in the water cycle."** Therefore, the correct answer is **D**.

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