Which of the following causes biomagni- fication

Options

A. `SO_2`
B. Mercury
C. DDT
D. Both (b) & (c)

Answer

### Step-by-Step Solution:

1. **Understanding Biomagnification**:
- Biomagnification is the process where the concentration of toxic substances increases in organisms at each successive trophic level. This means that as you move up the food chain, the levels of toxins become more concentrated.

2. **Identifying Toxic Substances**:
- Common substances known to cause biomagnification include heavy metals like mercury and certain pesticides like DDT (Dichlorodiphenyltrichloroethane). These substances are not easily metabolized or excreted by organisms, leading to accumulation.

3. **Analyzing the Options**:
- **Option A: Sulphur Oxide**: This is primarily an air pollutant and does not cause biomagnification.
- **Option B: Mercury**: This is a well-known toxic substance that causes biomagnification as it accumulates in organisms and increases in concentration at higher trophic levels.
- **Option C: DDT**: This pesticide is also known for causing biomagnification due to its persistence in the environment and accumulation in the food chain.
- **Option D: Both B and C**: Since both mercury and DDT are known to cause biomagnification, this option is correct.

4. **Conclusion**:
- The correct answer is **Option D: Both B and C**, as both mercury and DDT are substances that cause biomagnification.