…………refers to the increase in the concentration of toxicant like mercury at a successive level.

Options

A. Productivity
B. Biomagnification
C. Decomposition
D. Eutrophication

Answer

To solve the question regarding the increase in the concentration of toxicants like mercury at successive levels, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a term that describes the increase in concentration of toxic substances, such as mercury, as you move up the food chain.

2. **Analyze the Options**: The options provided are:
- Productivity
- Biomagnification
- Decomposition
- Eutrophication

3. **Evaluate Each Option**:
- **Productivity**: This term refers to the rate of biomass production in an ecosystem. It does not relate to the concentration of toxicants. Thus, this option is incorrect.
- **Biomagnification**: This term describes the process where the concentration of toxic substances increases as they move up the food chain. For example, small organisms absorb mercury, and when larger predators eat them, the mercury concentration increases in the predators. This is the correct option.
- **Decomposition**: This process involves breaking down complex organic matter into simpler substances. It does not pertain to the concentration of toxicants. Therefore, this option is incorrect.
- **Eutrophication**: This is the process of nutrient enrichment in water bodies, leading to excessive growth of algae. It is not related to the concentration of toxicants in food chains. Thus, this option is also incorrect.

4. **Conclusion**: After evaluating all options, the correct term that refers to the increase in the concentration of toxicants like mercury at successive levels is **Biomagnification**.

### Final Answer:
**Biomagnification**

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