Why is cold water poured over the heated metal rim which covers a wooden wheel?

Options

A. Because the rim contracts and fits over the wheel.
B. Because cold water is good for the life of the wheel.
C. Because the wooden wheel expands.
D. None of these

Explanation

To answer the question "Why is cold water poured over the heated metal rim which covers a wooden wheel?", we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- We have a wooden wheel and a metal rim that is designed to fit over the wheel.

2. **Initial Condition**:
- The radius of the metal rim is slightly smaller than that of the wooden wheel. This is important because it allows the rim to fit over the wheel after it has been heated.

3. **Heating the Metal Rim**:
- When the metal rim is heated, it expands. This is a physical property of metals; they tend to increase in size when their temperature rises.

4. **Fitting the Heated Rim**:
- After heating, the radius of the metal rim becomes approximately equal to the radius of the wooden wheel. At this point, the rim can be placed over the wheel.

5. **Cooling with Cold Water**:
- Once the heated metal rim is placed over the wooden wheel, cold water is poured over the rim. This is done to cool the metal rim quickly.

6. **Contraction of the Metal Rim**:
- As the metal rim cools down due to the cold water, it contracts. This contraction allows the rim to fit snugly over the wooden wheel, filling any gaps that may have existed when the rim was heated.

7. **Final Fit**:
- After the contraction, the metal rim fits perfectly over the wooden wheel, securing it in place.

### Conclusion:
The reason cold water is poured over the heated metal rim is to ensure that the rim contracts and fits securely over the wooden wheel.

### Answer:
**The correct answer is: Because the rim contracts and fits over the wheel.**

---