A person starts walking and comes back to its initial position after 2 h, then which of the following quantity is zero?

Options

A. Path length
B. Average speed
C. Displacement
D. Time

Answer

To solve the problem, let's analyze the situation step by step:

1. **Understanding the Motion**: The person starts walking from an initial position, moves away for some distance, and then returns to the initial position after 2 hours.

2. **Identifying the Quantities**: We need to determine which of the following quantities is zero:
- Path Length
- Average Speed
- Displacement

3. **Calculating Path Length**:
- The path length is the total distance traveled by the person.
- If the person walks a distance \( x \) away from the starting point and then returns the same distance \( x \), the total path length is:
\[ \text{Path Length} = x + x = 2x \]
- Therefore, the path length is not zero.

4. **Calculating Average Speed**:
- Average speed is defined as the total distance traveled divided by the total time taken.
- The total distance is \( 2x \) and the total time is 2 hours. Thus, the average speed is:
\[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} = \frac{2x}{2} = x \]
- Since \( x \) is a positive distance, the average speed is not zero.

5. **Calculating Displacement**:
- Displacement is defined as the change in position from the initial point to the final point.
- Since the person returns to the initial position, the final position is the same as the initial position. Therefore:
\[ \text{Displacement} = \text{Final Position} - \text{Initial Position} = 0 \]
- Thus, the displacement is zero.

6. **Conclusion**: Among the quantities considered, the only one that is zero is the displacement.

### Final Answer:
The quantity that is zero is **Displacement**.