Assertion : The position-time graph of a body moving uniformly is a straight line parallel to position-axis.
Reason : The slope of position-time graph in a uniform motion gives the velocity of an object.

Options

A. If both assertion and reason are trure and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanations of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason is false

Explanation

To solve the question regarding the assertion and reason about the position-time graph of a body moving uniformly, we will analyze both statements step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states: "The position-time graph of a body moving uniformly is a straight line parallel to the position-axis."
- In uniform motion, the position of the body changes at a constant rate. This means that the graph should show a linear relationship between position and time.
- A straight line parallel to the position-axis indicates that the position remains constant over time, which is not the case for uniform motion. Therefore, this assertion is **false**.

2. **Understanding the Reason**:
- The reason states: "The slope of the position-time graph in a uniform motion gives the velocity of an object."
- The slope of a position-time graph (dx/dt) represents the velocity of the object. In uniform motion, the velocity is constant, and thus the slope will also be constant.
- This statement is **true** because the slope indeed gives the velocity of the object in uniform motion.

3. **Conclusion**:
- Since the assertion is false and the reason is true, we can conclude that the correct option is:
- **C: Assertion is false but reason is true.**