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 human skin does not function as a respiratory organ, we will analyze each of the provided statements:

1. **Statement I: It is dry.**
- Human skin is indeed dry. This characteristic prevents effective gas exchange, which is essential for respiration. In contrast, amphibians like frogs have moist skin that allows for gas exchange.

2. **Statement II: It is not thick.**
- This statement is misleading. Human skin is actually relatively thick compared to the skin of some other organisms that can function in respiration. Thickness alone does not determine the ability to act as a respiratory organ.

3. **Statement III: It is not permeable to water and gases.**
- This statement is correct. Human skin is designed to be a barrier, preventing the passage of water and gases. This impermeability is crucial for maintaining homeostasis and protecting internal organs.

4. **Statement IV: It shows pigmentation.**
- This statement is not relevant to the skin's ability to function as a respiratory organ. Pigmentation serves primarily for protection against UV radiation and does not influence respiratory functions.

Based on the analysis, the statements that suggest reasons for human skin not functioning as a respiratory organ are:

- **Correct Statements:** I (It is dry), III (It is not permeable to water and gases).
- **Incorrect Statements:** II (It is not thick), IV (It shows pigmentation).

Thus, the correct option that includes the valid reasons is **"All except II and IV."**

### Final Answer:
The correct answer is **Option 2: All except IV.**