Assertion (A) : Work done in uniform circular motion is zero.
Reason (R) : Force is always directed along displacement .

Options

A. If both A and R are true and R is the correct explanation of A.
B. If both A and R are true but R is not the correct explanation of A.
C. If A is true but R is false
D. If A is false but R is true.

Explanation

To solve the problem, we need to analyze the assertion and the reason provided in the question.

### Step-by-Step Solution:

1. **Understanding Uniform Circular Motion**:
- In uniform circular motion, an object moves in a circular path with a constant speed. However, its direction changes continuously.

2. **Identifying the Forces**:
- The force acting on the object in uniform circular motion is the centripetal force, which always points towards the center of the circular path.

3. **Direction of Displacement**:
- The displacement of the object at any point in time is tangential to the circular path. This means that while the object moves, its displacement vector is directed along the tangent to the circle.

4. **Calculating Work Done**:
- Work done (W) is calculated using the formula:
\[ W = F \cdot d \cdot \cos(\theta) \]
- Here, \(F\) is the force, \(d\) is the displacement, and \(\theta\) is the angle between the force and the displacement vectors.

5. **Finding the Angle**:
- In uniform circular motion, the angle \(\theta\) between the centripetal force (directed towards the center) and the displacement (tangential) is \(90^\circ\).

6. **Substituting the Angle**:
- Since \(\cos(90^\circ) = 0\), we can substitute this into the work done formula:
\[ W = F \cdot d \cdot \cos(90^\circ) = F \cdot d \cdot 0 = 0 \]
- Therefore, the work done in uniform circular motion is zero.

7. **Evaluating the Assertion**:
- The assertion states that "Work done in uniform circular motion is zero." This is correct based on our calculations.

8. **Evaluating the Reason**:
- The reason states that "Force is always directed along displacement." This is incorrect because, in uniform circular motion, the force is directed towards the center of the circle, while the displacement is tangential.

9. **Conclusion**:
- The assertion (A) is true, while the reason (R) is false. Therefore, the correct answer is that A is true and R is false.

### Final Answer:
Assertion (A) is true, and Reason (R) is false.