Assertion : `L//R and CR` both have same dimensions
Reason `L//R and CR` both have dimensions of time

Options

A. If both Assertion and Reason are correct and Reason is the correct explaination of Assertion.
B. If both Assertion and Reason are correct but Reason is not the correct explaination of Assertion.
C. If Assertion is true but Reason is false.
D. If Assertion is false but Reason is true.

Explanation

To solve the problem, we need to analyze the assertion and the reason provided, focusing on the dimensions of the quantities involved.

### Step-by-Step Solution:

1. **Identify the Dimensions of L and R**:
- The dimension of \( L \) is given as:
\[ [L] = M^1 L^2 T^{-2} A^{-2} \]
- The dimension of \( R \) is given as:
\[ [R] = M^1 L^2 T^{-3} A^{-2} \]

2. **Calculate the Dimension of \( \frac{L}{R} \)**:
- To find the dimension of \( \frac{L}{R} \):
\[ \frac{L}{R} = \frac{M^1 L^2 T^{-2} A^{-2}}{M^1 L^2 T^{-3} A^{-2}} \]
- Simplifying this:
- The \( M^1 \) cancels out: \( M^{1-1} = M^0 \)
- The \( L^2 \) cancels out: \( L^{2-2} = L^0 \)
- For time \( T \): \( T^{-2} - (-3) = T^{1} \)
- The \( A^{-2} \) cancels out: \( A^{-2} - (-2) = A^0 \)
- Therefore, the dimension of \( \frac{L}{R} \) is:
\[ \left[\frac{L}{R}\right] = M^0 L^0 T^1 A^0 = T^1 \]

3. **Identify the Dimension of C**:
- The dimension of \( C \) is given as:
\[ [C] = M^{-1} L^{-2} T^4 A^2 \]

4. **Calculate the Dimension of \( CR \)**:
- To find the dimension of \( CR \):
\[ CR = C \times R = (M^{-1} L^{-2} T^4 A^2) \times (M^1 L^2 T^{-3} A^{-2}) \]
- Simplifying this:
- For mass \( M \): \( M^{-1} + 1 = M^0 \)
- For length \( L \): \( L^{-2} + 2 = L^0 \)
- For time \( T \): \( T^{4 - 3} = T^{1} \)
- For charge \( A \): \( A^{2 - 2} = A^0 \)
- Therefore, the dimension of \( CR \) is:
\[ [CR] = M^0 L^0 T^1 A^0 = T^1 \]

5. **Conclusion**:
- We have found that both \( \frac{L}{R} \) and \( CR \) have the same dimensions:
\[ \left[\frac{L}{R}\right] = [CR] = T^1 \]
- Thus, the assertion that \( \frac{L}{R} \) and \( CR \) both have the same dimensions is **true**.
- The reason that both \( \frac{L}{R} \) and \( CR \) have dimensions of time is also **true**.

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