[A]: Repeated use of CT scanning is harmful.
[R]: IN CT scanning. X-ray is used.

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

### Step-by-Step Solution

1. **Understanding the Assertion (A)**: The assertion states that repeated use of CT scanning is harmful. This is a valid statement as repeated exposure to certain types of radiation can have adverse health effects.

2. **Understanding the Reason (R)**: The reason provided states that in CT scanning, X-ray is used. This is also true since CT scans utilize X-ray technology to create detailed images of the body's internal structures.

3. **Linking A and R**: The assertion (A) is about the harmful effects of repeated CT scans, while the reason (R) explains the mechanism (use of X-rays) behind CT scanning.

4. **Evaluating the Harmfulness**: It is important to note that X-rays are a form of ionizing radiation. Repeated exposure to ionizing radiation can increase the risk of developing cancer over time. This supports the assertion that repeated use of CT scans can be harmful.

5. **Conclusion**: Since both the assertion and the reason are true, and the reason correctly explains why the assertion is true, we conclude that both statements are correct and the reason is a correct explanation of the assertion.

### Final Answer
Both the assertion (A) and the reason (R) are true, and R is a correct explanation of A.

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