Which of the following statements suggest the reason for the skin of humans to not perform as the respiratory organ?
(I) It is dry
(II) If is not thick
(III) It is not permeable to water and gases
(IV) It shows pigmentation

Options

A. All except III
B. All except IV
C. All except I and III
D. All except I and IV

Answer

To determine why the skin of humans does not function as a respiratory organ, we need to analyze each statement provided:

1. **Statement I: It is dry.**
- Human skin is indeed dry compared to the moist skin of amphibians, which allows them to respire through their skin. The dryness of human skin limits its ability to facilitate gas exchange effectively.

2. **Statement II: It is not thick.**
- This statement is somewhat misleading. While the thickness of skin can affect its ability to function as a respiratory organ, human skin is actually composed of multiple layers (epidermis, dermis, etc.), which can be considered thick. However, the primary reason for not functioning as a respiratory organ is not solely based on thickness.

3. **Statement III: It is not permeable to water and gases.**
- This statement is true. Human skin acts as a barrier and is not permeable to gases and water in the same way that the skin of amphibians is. This impermeability prevents effective gas exchange, which is essential for respiration.

4. **Statement IV: It shows pigmentation.**
- This statement is not relevant to the function of skin as a respiratory organ. Pigmentation does not affect the skin's ability to exchange gases and is not a reason for the skin's inability to perform respiratory functions.

**Conclusion:**
Based on the analysis, the statements that suggest reasons for the skin of humans not performing as a respiratory organ are:
- I (It is dry)
- III (It is not permeable to water and gases)

Therefore, the correct option is that all statements except IV are valid reasons.