Which of the following are the harmful effects of nitrogen oxide?
It retards the rate of photosynthesis.
It causes respiratory disease in children.
It is toxic to living tissues.

Options

A. I and II
B. II and III
C. I and III
D. All of these

Answer

To determine the harmful effects of nitrogen oxide (NO2), we will analyze each of the three statements provided in the question.

### Step 1: Analyze the first statement
The first statement claims that nitrogen oxide retards the rate of photosynthesis.
- **Explanation**: Nitrogen oxide, particularly in the form of nitrogen dioxide (NO2), can damage plant leaves. When the leaves are damaged, their ability to perform photosynthesis is hindered, leading to a decrease in the overall rate of photosynthesis in plants.
- **Conclusion**: This statement is true.

### Step 2: Analyze the second statement
The second statement states that nitrogen oxide causes respiratory diseases in children.
- **Explanation**: Nitrogen oxides are known lung irritants. Exposure to high levels of nitrogen oxides can lead to respiratory issues, particularly in vulnerable populations such as children. This includes conditions like asthma and other acute respiratory diseases.
- **Conclusion**: This statement is also true.

### Step 3: Analyze the third statement
The third statement asserts that nitrogen oxide is toxic to living tissues.
- **Explanation**: Nitrogen oxides are indeed toxic to living tissues. They can cause irritation and damage to the respiratory tract and other bodily tissues. This toxicity extends to various biological systems, making it a harmful pollutant.
- **Conclusion**: This statement is true as well.

### Final Conclusion
All three statements regarding the harmful effects of nitrogen oxide are correct:
1. It retards the rate of photosynthesis.
2. It causes respiratory disease in children.
3. It is toxic to living tissues.

Therefore, the correct answer to the question is that all of these are harmful effects of nitrogen oxide.