A: Photochemical smog is also known as oxidising smog.
R: Photochemical smog is chiefly composed of `O_(3)` PAN, etc.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To analyze the given statements about photochemical smog, we will break down the assertion (A) and the reason (R) step by step.

### Step 1: Understanding Assertion (A)
**Assertion (A): Photochemical smog is also known as oxidizing smog.**

Photochemical smog is formed when sunlight reacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx). This reaction produces a mixture of pollutants, including ozone (O3), which is a strong oxidizing agent. Therefore, it is accurate to refer to photochemical smog as oxidizing smog due to the presence of ozone and other oxidants.

### Step 2: Understanding Reason (R)
**Reason (R): Photochemical smog is chiefly composed of O3, PAN, etc.**

Photochemical smog primarily consists of ozone (O3) and peroxyacetyl nitrate (PAN), among other components. Ozone is formed through the photochemical reactions of pollutants, and PAN is a secondary pollutant formed in the atmosphere. The presence of these compounds confirms that photochemical smog is indeed composed of oxidizing agents.

### Step 3: Evaluating the Relationship Between A and R
Both the assertion and the reason are true statements. The reason provides a correct explanation for the assertion because the composition of photochemical smog (which includes O3 and PAN) supports the classification of photochemical smog as oxidizing smog.

### Conclusion
Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

### Final Answer
Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.

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