Eutrophication of often seen in:

Options

A. Mountains
B. Deserts
C. Fresh water lakes
D. Ocean

Answer

### Step-by-Step Solution:

1. **Understanding Eutrophication**:
- Eutrophication is a process characterized by the excessive growth of algae and aquatic plants due to nutrient enrichment in water bodies.

2. **Identifying the Environment**:
- Eutrophication is most commonly observed in freshwater ecosystems, particularly in freshwater lakes.

3. **Reasons for Eutrophication in Freshwater Lakes**:
- Freshwater lakes often receive a variety of nutrients from agricultural runoff, sewage discharge, and other sources, which leads to nutrient enrichment.

4. **Effects of Eutrophication**:
- The nutrient enrichment causes rapid growth of certain species, particularly algae. This algal bloom can cover the surface of the water, blocking sunlight from reaching other aquatic plants.

5. **Consequences on Biodiversity**:
- As algae proliferate, they consume oxygen in the water when they die and decompose, leading to hypoxic conditions (low oxygen levels). This results in the death of other aquatic organisms, thereby reducing species diversity.

6. **Conclusion**:
- Based on the understanding of eutrophication and its effects, the correct answer to the question is that eutrophication is often seen in **freshwater lakes**.