Evidence for the reptilian origin of birds is the occurrence of
(a) Scales
(b) Hairs
(c) Claws
(d) Feathers

Options

A. Scales
B. Hairs
C. Claws
D. Feathers

Answer

To solve the question regarding the evidence for the reptilian origin of birds, we will analyze each option provided:

1. **Understanding the Question**: The question asks for evidence that supports the idea that birds have evolved from reptiles. We need to identify which of the given options serves as this evidence.

2. **Evaluating Each Option**:
- **(a) Scales**: Birds possess scales on their legs and feet, similar to those found in reptiles. This characteristic supports the theory that birds have a common ancestry with reptiles.
- **(b) Hairs**: Hairs are a characteristic of mammals, not reptiles. Therefore, this option does not provide evidence for the reptilian origin of birds.
- **(c) Claws**: While birds do have claws, they are not unique to reptiles as they are also found in many other animal groups. Claws do not specifically indicate a reptilian origin.
- **(d) Feathers**: Feathers are a unique characteristic of birds and do not provide evidence of a reptilian origin. In fact, feathers are considered an adaptation that evolved in birds.

3. **Conclusion**: Based on the analysis, the presence of scales (option a) is the most significant evidence supporting the reptilian origin of birds. Therefore, the correct answer is **(a) Scales**.

### Summary of Steps:
1. Read and understand the question.
2. Analyze each option for its relevance to the reptilian origin of birds.
3. Identify that scales are present in both birds and reptiles, supporting the evolutionary link.
4. Conclude that the correct answer is (a) Scales.