(A) : Voltmeter put across a part of the circuit, it reads slightly less than the original voltage.
(R) : Voltmeter is always connected in parallel in circuit across which voltage is to be measured.

Options

A. Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'.
B. Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'
C. 'A' is true and 'R' is false
D. 'A' is false and 'R' is false

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided:

### Step 1: Understand the Assertion (A)
The assertion states that "Voltmeter put across a part of the circuit, it reads slightly less than the original voltage."

- **Analysis**: This statement is generally true. When a voltmeter is connected across a part of a circuit, it can read a voltage that is slightly less than the actual voltage due to its internal resistance. This is because the voltmeter itself draws some current, which can affect the voltage across the component it is measuring.

### Step 2: Understand the Reason (R)
The reason states that "Voltmeter is always connected in parallel in the circuit across which voltage is to be measured."

- **Analysis**: This statement is true. A voltmeter is designed to measure the potential difference (voltage) across two points in a circuit, and it must be connected in parallel to do so. This is a fundamental principle of how voltmeters operate.

### Step 3: Determine the Relationship Between A and R
Now we need to determine if the reason (R) correctly explains the assertion (A).

- **Analysis**: While both A and R are true, R does not explain why A is true. The reason for the voltmeter reading slightly less than the original voltage is due to its internal resistance affecting the circuit, not merely because it is connected in parallel.

### Conclusion
- **Final Assessment**:
- Assertion (A) is true.
- Reason (R) is true.
- However, R is not the correct explanation for A.

Thus, the correct answer is that both A and R are true, but R is not the correct explanation of A.

### Answer
Both A and R are true, but R is not the correct explanation of A.

---