Which of the following conditions shows the polluted enviorment ?

Options

A. pH of rain water 5.6
B. Amount of carbon dioxide in the atmosphere is `0.03%`
C. Biochemical oxygen demand `10 "ppm"`
D. Eutrophication

Explanation

To determine which conditions indicate a polluted environment, let's analyze each option step by step.

### Step 1: Analyze the first condition
- **Condition A**: pH of rainwater is 5.6.
- The normal pH of rainwater is around 6. A pH of 5.6 is slightly acidic but not significantly so. Acidic rain is typically defined as having a pH below 5.6. Therefore, this condition does not indicate pollution.

**Conclusion for A**: Not polluted.

### Step 2: Analyze the second condition
- **Condition B**: Amount of carbon dioxide in the atmosphere is 0.03%.
- The normal concentration of carbon dioxide in the atmosphere is around 0.04%. Since 0.03% is below this threshold, it indicates a non-polluted environment.

**Conclusion for B**: Not polluted.

### Step 3: Analyze the third condition
- **Condition C**: Biochemical oxygen demand (BOD) is 10 ppm.
- BOD measures the amount of organic waste in water. A BOD of less than 5 ppm indicates clean water, while a BOD above 15-17 ppm indicates heavily polluted water. A BOD of 10 ppm suggests moderate pollution since it is above the clean threshold.

**Conclusion for C**: Polluted.

### Step 4: Analyze the fourth condition
- **Condition D**: Eutrophication.
- Eutrophication is a process where excess nutrients in water bodies lead to algal blooms, which consume dissolved oxygen and create anaerobic conditions. This results in the death of fish and other aquatic life, indicating a severely polluted environment.

**Conclusion for D**: Polluted.

### Final Conclusion
Based on the analysis:
- **Condition C (BOD = 10 ppm)** and **Condition D (Eutrophication)** indicate a polluted environment.

### Final Answer
The correct answers are **C and D**.

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