Correct statement about smog is:

Options

A. Both `NO_2` and` SO_2 `are present in classical smog.
B. Classical smog also has high concentration of oxidizing agents
C. `NO_2` is present in classical smog.
D. Photochemical smog has high concentration of oxidizing agents.

Answer

To determine the correct statement about smog, we need to analyze each option provided in the question. Here’s a step-by-step breakdown of the analysis:

### Step 1: Analyze the first statement
**Statement:** Both NO2 and SO2 are present in classical smoke.

**Analysis:** Classical smoke is characterized by the presence of smoke, fog, and sulfur dioxide (SO2). However, nitrogen dioxide (NO2) is not typically associated with classical smoke. Therefore, this statement is **incorrect**.

### Step 2: Analyze the second statement
**Statement:** Classical smoke also has a high concentration of oxidizing agents.

**Analysis:** Classical smoke is known to contain reducing agents, such as sulfur dioxide (SO2), which can act as a reducing agent. It does not have a high concentration of oxidizing agents. Thus, this statement is also **incorrect**.

### Step 3: Analyze the third statement
**Statement:** NO2 is present in classical smoke.

**Analysis:** As established earlier, classical smoke primarily consists of smoke, fog, and SO2. NO2 is not a component of classical smoke. Therefore, this statement is **incorrect**.

### Step 4: Analyze the fourth statement
**Statement:** Photochemical smoke has a high concentration of oxidizing agents.

**Analysis:** Photochemical smog is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. This process leads to the formation of ozone (O3) and other oxidizing agents. Therefore, this statement is **correct**.

### Conclusion
The correct statement about smog is: **Photochemical smoke has a high concentration of oxidizing agents.**

### Final Answer
The correct option is **Option 4**.

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