Why cockroach blood does not contain respiratory pigment?
I. It does not respire.
II. It respires anaerobically.
III. Oxygen passes to all the tissue through diffusion.
IV. Oxygen reaches tissue through tracheoles.
Choose the correct options.

Options

A. Only I
B. Only II
C. Only IV
D. III and IV

Answer

To answer the question "Why does cockroach blood not contain respiratory pigment?", we need to analyze each of the provided statements.

1. **Statement I: It does not respire.**
- This statement is incorrect. Cockroaches do respire, but they do so through a different mechanism than mammals.

2. **Statement II: It respires anaerobically.**
- This statement is also incorrect. While cockroaches can survive in low oxygen environments, they primarily respire aerobically using oxygen.

3. **Statement III: Oxygen passes to all the tissues through diffusion.**
- This statement is correct. In cockroaches, oxygen is delivered to tissues through the process of diffusion.

4. **Statement IV: Oxygen reaches tissue through tracheoles.**
- This statement is correct. Cockroaches have a tracheal system that transports oxygen directly to their tissues via tracheoles.

Based on the analysis, the correct options are **III and IV**.

### Step-by-Step Solution:
1. **Evaluate Statement I**: Determine if cockroaches respire.
- Cockroaches do respire, so this statement is false.

2. **Evaluate Statement II**: Check if cockroaches respire anaerobically.
- Cockroaches primarily respire aerobically, making this statement false.

3. **Evaluate Statement III**: Assess if oxygen passes to tissues through diffusion.
- This is true; oxygen does diffuse to tissues.

4. **Evaluate Statement IV**: Confirm if oxygen reaches tissues through tracheoles.
- This is also true; the tracheal system allows for oxygen transport.

5. **Conclusion**: Identify the correct statements.
- The correct options are III and IV.