Which of the following statements is correct ?

Options

A. Primary pollutants are more harmful than secondary pollutants.
B. Primary pollutants ans secondary pollutants are equally harmful.
C. Secondary pollutants are more harmful than primary pollutants.
D. DDT is a secondary pollutant.

Explanation

To determine which statement is correct regarding primary and secondary pollutants, we can analyze each statement step by step.

### Step 1: Understand the Definitions
- **Primary Pollutants**: These are pollutants that are emitted directly from a source. Examples include carbon monoxide, sulfur dioxide, and particulate matter.
- **Secondary Pollutants**: These are not emitted directly. Instead, they form in the atmosphere through chemical reactions between primary pollutants. An example is ozone, which forms from the reaction of sunlight with pollutants like volatile organic compounds (VOCs) and nitrogen oxides.

**Hint**: Remember the difference between direct emissions (primary) and reactions that create new pollutants (secondary).

### Step 2: Analyze the First Statement
- The first statement claims that primary pollutants are more harmful than secondary pollutants. This is incorrect because secondary pollutants can be more harmful due to their toxic nature and the complex reactions that create them.

**Hint**: Consider the nature and toxicity of pollutants when comparing their harmful effects.

### Step 3: Analyze the Second Statement
- The second statement suggests that primary pollutants are secondary pollutants and are equally harmful. This is also incorrect. Primary pollutants are distinct from secondary pollutants, and they are not the same.

**Hint**: Focus on the definitions of primary and secondary pollutants to evaluate their relationship.

### Step 4: Analyze the Third Statement
- The third statement states that secondary pollutants are more harmful than primary pollutants. This is true. Secondary pollutants often have more severe health and environmental impacts due to their chemical properties and the reactions that create them.

**Hint**: Think about real-world examples of secondary pollutants and their effects on health and the environment.

### Step 5: Analyze the Fourth Statement
- The fourth statement mentions DDT as a primary pollutant. While DDT is indeed a pollutant, it does not fit the definition of a secondary pollutant. This statement is misleading because it does not correctly categorize DDT.

**Hint**: Recall that not all pollutants fit neatly into primary or secondary categories, and some may have historical significance.

### Conclusion
After analyzing all the statements, the only correct statement is that secondary pollutants are more harmful than primary pollutants.

**Final Answer**: The correct statement is: "Secondary pollutants are more harmful than primary pollutants."