A : A body moving with decreasing speed may have increasing acceleration.
R : The speed of body decreases, when acceleration of body is opposite to velocity.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statement, then mark (4).

Answer

To solve the problem, we need to analyze the assertion and reason provided:

**Assertion (A):** A body moving with decreasing speed may have increasing acceleration.
**Reason (R):** The speed of a body decreases when the acceleration of the body is opposite to the velocity.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that a body can be moving with decreasing speed while still having increasing acceleration.
- To clarify, acceleration is defined as the rate of change of velocity. If a body is moving in one direction (say, positive velocity) and the acceleration is in the opposite direction (negative acceleration), the speed of the body will decrease.

2. **Analyzing the Reason:**
- The reason provided states that the speed of a body decreases when the acceleration is opposite to the velocity.
- This statement is indeed true. When the acceleration acts in the opposite direction to the velocity, it reduces the speed of the body.

3. **Connecting the Assertion and Reason:**
- If the body has a positive velocity and negative acceleration, the speed decreases. However, if the magnitude of acceleration is increasing (becoming more negative), the rate at which speed decreases is increasing, which means the acceleration is increasing in the negative direction.
- Hence, it is possible for a body to have decreasing speed while experiencing increasing (in magnitude) acceleration.

4. **Conclusion:**
- Both the assertion and the reason are true.
- The reason correctly explains the assertion because it describes the condition under which the speed decreases.

### Final Answer:
Both assertion and reason are true, and the reason is the correct explanation of the assertion. Therefore, the correct option is **1**.

---