Assertion (A): As the relaxation time Increases drift velocity increases.
Reason (R):`V_(d) prop tau`

Options

A. Both (A) and (R) are true and (R) is the correct explanation of (A).
B. Both (A) and (R) are true but (R) is not the correct explanation of (A).
C. (A) is true but (R) is false.
D. (A) is false and (R) is also false.

Explanation

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states: "As the relaxation time increases, drift velocity increases."

- **Drift Velocity (V_d)** is defined as the average velocity that a charged particle, such as an electron, attains due to an electric field.
- **Relaxation Time (τ)** is the average time between collisions of the charge carriers (like electrons) in a conductor.

### Step 2: Understand the Reason
The reason states: "V_d is directly proportional to τ."

- The relationship can be expressed mathematically as:
\[ V_d = \frac{E \cdot τ}{m} \]
where \(E\) is the electric field and \(m\) is the mass of the charge carrier.

### Step 3: Analyze the Relationship
From the equation \(V_d = \frac{E \cdot τ}{m}\), we can see that:

- If the electric field \(E\) and mass \(m\) are constant, then \(V_d\) is directly proportional to τ.
- This means that as τ increases, \(V_d\) also increases.

### Step 4: Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, we can conclude:

- **Assertion (A)**: True
- **Reason (R)**: True and is the correct explanation of (A).

### Final Answer
Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

---