[A]: Some babies have a small tail.
[R]: This is just a freak of nature and has no explanation

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, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that some babies have a small tail. This phenomenon, although rare, is indeed observed in certain cases where babies are born with a small tail-like structure.

**Hint**: Think about rare genetic occurrences and their implications in biology.

2. **Understanding the Reason (R)**: The reason claims that this occurrence is just a freak of nature and has no explanation. However, this statement is misleading. The presence of a small tail in some babies can be explained through the concept of atavism, which refers to the reappearance of traits from ancestral species.

**Hint**: Consider the concept of atavism and how it relates to evolutionary biology.

3. **Connecting A and R**: Since the assertion is true (some babies do have small tails), but the reason provided is false (it does have an explanation in terms of atavism), we can conclude that the assertion is correct while the reason is incorrect.

**Hint**: Evaluate the relationship between the assertion and the reason critically.

4. **Final Conclusion**: Based on the analysis, the correct answer is that assertion A is true, but reason R is false.

**Hint**: Look for answer options that reflect the truth of A and the falsehood of R.

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