[A]: While undergoing MRI, patients having pacemaker should take some care.
[R]: MRI does not affect pacemaker.

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 and R is false
D. If both A and R are false

Answer

To solve the question regarding the assertion and reason about patients with pacemakers undergoing MRI, we will analyze both statements step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states: "While undergoing MRI, patients having pacemaker should take some care."
- MRI (Magnetic Resonance Imaging) uses strong magnetic fields and radio waves to create detailed images of the organs and tissues inside the body.
- Patients with pacemakers need to be cautious because the strong magnetic fields can interfere with the functioning of the pacemaker.

2. **Evaluating the Reason (R)**:
- The reason states: "MRI does not affect pacemaker."
- This statement is misleading. In reality, MRI can potentially affect the functioning of a pacemaker. The magnetic fields can cause the pacemaker to malfunction or even be damaged.

3. **Conclusion on Assertion and Reason**:
- The assertion (A) is true because patients with pacemakers must take precautions during an MRI.
- The reason (R) is false because MRI can indeed affect pacemakers.

4. **Determining the Correct Option**:
- Based on the evaluation, we find that:
- A is true (patients with pacemakers should take care during MRI).
- R is false (MRI does affect pacemakers).
- Therefore, the correct option is C: "If A is true and R is false."

### Final Answer:
The correct option is C: "A is true and R is false."