Which of the following compounds are well known for biological magnification?

Options

A. DDT
B. Mercury
C. methane
D. both(1)(2)

Answer

### Step-by-Step Solution:

1. **Understanding Biological Magnification**:
- Biological magnification, also known as biomagnification, refers to the process where the concentration of toxic substances increases in organisms at each successive trophic level of a food chain.

2. **Identifying the Compounds**:
- We need to evaluate the given compounds:
- **DDT (Dichloro-Diphenyl-Trichloroethane)**: A pesticide that is known to accumulate in the fatty tissues of organisms and is notorious for causing harm to wildlife, particularly birds.
- **Mercury**: A heavy metal that can accumulate in living organisms and is known for its neurotoxic effects, especially in aquatic ecosystems.
- **Methane**: A greenhouse gas that is not known for biomagnification; it does not accumulate in the same way as DDT or mercury.

3. **Analyzing the Options**:
- Option A: DDT - Known for biomagnification.
- Option B: Mercury - Also known for biomagnification.
- Option C: Methane - Not associated with biomagnification.
- Option D: Both A and B - This option includes both DDT and mercury, both of which are known for biomagnification.

4. **Conclusion**:
- Since both DDT and mercury are well-known compounds that undergo biological magnification, the correct answer is **Option D: Both A and B**.