The greater BOD of waste water

Options

A. Increases oxygen content of water
B. Decreases oxygen content of water
C. Relates the decreases of temperature of water
D. all of these

Answer

### Step-by-Step Solution:

1. **Understanding BOD**: BOD stands for Biological Oxygen Demand. It is a measure of the amount of oxygen that microorganisms will consume while decomposing organic matter in water.

2. **Impact of Organic Matter**: When wastewater contains a high amount of organic matter (like sewage), it leads to a higher BOD. This indicates that there is a greater demand for oxygen by the microorganisms that break down this organic matter.

3. **Oxygen Consumption**: As microorganisms consume oxygen to decompose the organic matter, the amount of dissolved oxygen (DO) in the water decreases. This is because the oxygen is being used up by these microorganisms.

4. **Consequences for Aquatic Life**: A lower amount of dissolved oxygen in the water can be detrimental to aquatic life, particularly for higher animals like fish, which require sufficient oxygen to survive.

5. **Conclusion**: Therefore, when there is a greater BOD in wastewater, it results in a decrease in the oxygen content of the water. Thus, the correct answer to the question is option B: "decreases oxygen content of water."

### Final Answer:
**Option B: Decreases oxygen content of water.**

---