Respiratory system is derived from

Options

A. Ectoderm
B. Mesoderm
C. Endoderm
D. Chorda mesoderm.

Answer

### Step-by-Step Solution:

1. **Understanding Germ Layers**:
- The human body is developed from three primary germ layers: ectoderm, mesoderm, and endoderm. Each layer gives rise to different systems and organs in the body.

2. **Identifying the Germ Layers**:
- **Ectoderm**: This layer is primarily responsible for forming the nervous system (including the brain and spinal cord), sense organs, and the outer layer of skin (epidermis).
- **Mesoderm**: This layer contributes to the formation of muscles, bones, gonads, and connective tissues.
- **Endoderm**: This layer is crucial for forming the internal structures, including the gut tube, liver, and respiratory system.

3. **Focusing on the Respiratory System**:
- The question specifically asks about the origin of the respiratory system. According to developmental biology, the respiratory system, including structures like the lungs, is derived from the endoderm.

4. **Conclusion**:
- Based on the information about the germ layers and their contributions to the body, the respiratory system is derived from the endoderm. Therefore, the correct answer is **option C: endoderm**.