Which is not detectable in birds ?

Options

A. Pectoral girdle
B. Pelvic girdle
C. Fore limbs
D. Hind limbs

Answer

To solve the question "Which is not detectable in birds?" we will analyze the options provided and understand the anatomy of birds.

### Step-by-step Solution:

1. **Understanding Bird Anatomy**: Birds are vertebrates with a specialized skeletal structure. They possess a vertebral column, a hollow dorsal nerve cord, and certain features like pharyngeal gill slits during some stages of their life.

2. **Identifying Limbs**: Birds have two pairs of limbs. The forelimbs are modified into wings, which are essential for flight, while the hind limbs are used for walking, perching, or swimming in some species.

3. **Analyzing the Options**:
- **Pectoral Girdle**: This is the structure that supports the forelimbs (wings) in birds. It is detectable.
- **Pelvic Girdle**: This supports the hind limbs and is also detectable.
- **Fore Limbs**: In birds, these are modified into wings. While they exist, they are not detectable in the same way as traditional limbs because they serve a different function.
- **Hind Limbs**: These are the legs of the bird and are definitely detectable.

4. **Conclusion**: Since the forelimbs are modified into wings and do not function as traditional limbs, they are not detectable in the same way as other limbs. Thus, the correct answer is **fore limbs**.

### Final Answer:
The option that is not detectable in birds is **fore limbs**.

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