When a person walks on a rough surface, the frictional force exerted by surface on the person is opposite to the direction of his motion.
It is the force exerted by the road on the person that causes the motion.

Options

A. (a)Both Assertion and Reason are true and the reason is correct explanation of the Assertion.
B. (b)Both Assertion and Reason are true but reason is not the correct explanation of Assertion.
C. (c)Assertion is true, but the Reason is false.
D. (d)Assertion is false but the Reason is true.

Explanation

To solve the question, we need to analyze the two statements provided and determine their validity based on the principles of physics, particularly the concept of friction and motion.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "the frictional force exerted by the surface on the person is opposite to the direction of his motion."
- When a person walks, their foot pushes backward against the ground. According to Newton's third law, the ground exerts an equal and opposite force (friction) on the foot.

**Hint**: Think about how friction works in relation to motion.

2. **Analyzing the Direction of Forces**:
- When the foot pushes backward, the frictional force acts forward on the foot to oppose the backward motion. This forward frictional force is what propels the person forward.
- Therefore, the frictional force is actually in the same direction as the person's motion, not opposite.

**Hint**: Visualize the motion of walking and how forces are applied.

3. **Understanding the Reason**:
- The reason states that "it is the force exerted by the road on the person that causes the motion."
- This statement is true because the frictional force (which is a reaction force from the ground) is what allows the person to move forward.

**Hint**: Consider the role of the ground in providing the necessary force for walking.

4. **Evaluating the Truth of Each Statement**:
- Since the assertion is false (the frictional force is not opposite to the motion but in the same direction), and the reason is true (the frictional force from the ground causes the motion), we conclude:
- Assertion: False
- Reason: True

**Hint**: Compare the assertion and reason to determine their truth values.

5. **Choosing the Correct Option**:
- Based on the evaluation, the correct answer is that the assertion is false, but the reason is true. This corresponds to option D.

**Hint**: Review the options carefully to ensure you select the one that matches your findings.

### Final Answer:
The correct answer is option D: "Assertion is false but the reason is true."