Three water samples namely river water, untreated sewage water and secondary effluent discharge from a sewage treatment plant were subjected to BOD test. The samples were labelled A,B and C. but the laboratory attened did not note, which was which . The BOD values of the three samples A,B and C were recorded as 20 mg/L , 8 mg/L and 400 mg/L, respectively. which sample of the water is most polluted ? can you assign the correct label to each , assuming the river water is relatively clean

Explanation

To determine which water sample is the most polluted based on the BOD (Biochemical Oxygen Demand) values provided, we can follow these steps:

### Step-by-Step Solution:

1. **Understand BOD**: BOD is a measure of the amount of dissolved oxygen that aerobic bacteria will consume while decomposing organic matter in water. Higher BOD values indicate higher levels of organic pollution.

2. **Analyze the BOD Values**: The BOD values for the three samples are:
- Sample A: 20 mg/L
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