A baby has been born with a small tail. It is case exhibiting `:`

Options

A. Retrogressive evolution
B. Mutation theory is wrong
C. Atavism
D. Metramorphosis

Answer

To solve the question, we need to understand the concept of atavism and how it relates to the situation described.

### Step-by-Step Solution:

1. **Identify the Situation**: The question states that a baby has been born with a small tail. This is an unusual characteristic for modern humans, as tails are not present in the majority of the population.

2. **Understand Ancestral Traits**: The presence of a tail in the baby suggests that this trait was present in some of our distant ancestors. Over time, as species evolve, certain traits may diminish or disappear, but they can occasionally reappear in descendants.

3. **Define Atavism**: Atavism refers to the reappearance of ancestral traits that had previously disappeared or been reduced in a lineage. In this case, the small tail is an example of an ancestral trait that has reappeared in the baby.

4. **Conclusion**: Since the baby exhibits a trait (the tail) that is reminiscent of a characteristic found in ancestral species, we conclude that this case is exhibiting atavism.

5. **Final Answer**: The correct answer is that the baby is exhibiting atavism.