To determine which statement is true about photochemical smog, we can analyze the characteristics and effects of photochemical smog step by step.
### Step-by-Step Solution:
1. **Definition of Photochemical Smog**:
Photochemical smog is a type of air pollution that is formed when sunlight reacts with pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). This reaction produces secondary pollutants like ozone (O3) and other harmful compounds.
**Hint**: Remember that photochemical smog is primarily formed through reactions involving sunlight and specific pollutants.
2. **Conditions for Formation**:
Photochemical smog typically occurs in warm, dry, and sunny climates. The presence of sunlight is crucial for the photochemical reactions to take place.
**Hint**: Think about the weather conditions that would facilitate the formation of smog.
3. **Components of Photochemical Smog**:
The main components of photochemical smog include nitrogen dioxide (NO2) and ozone (O3). These compounds are formed during the reaction of sunlight with pollutants.
**Hint**: Identify the key pollutants involved in the formation of photochemical smog.
4. **Health Effects**:
Photochemical smog can cause various health issues, including irritation of the eyes, nose, and throat. It can also lead to headaches, chest pain, and difficulty in breathing.
**Hint**: Consider the impact of smog on human health and respiratory systems.
5. **Evaluating Statements**:
Now, we can evaluate the options provided in the question:
- **Option A**: Incorrect - Photochemical smog is not reducing in nature.
- **Option B**: Incorrect - It is not formed in water; it forms in the atmosphere.
- **Option C**: Correct - It occurs in warm, dry, and sunny climates.
- **Option D**: Correct - It causes irritation in the eyes, nose, and throat.
**Hint**: Carefully analyze each option against the characteristics and effects of photochemical smog.
### Conclusion:
The correct statements regarding photochemical smog are:
- It occurs in warm, dry, and sunny climates (Option C).
- It causes irritation in the eyes, nose, and throat (Option D).
Thus, the true statement about photochemical smog is that it causes irritation in the eyes, nose, and throat.
**Final Answer**: Option D is correct.
