Open drain system is a breeding place for which of the following.

Options

A. Flies
B. Mosquitoes
C. Organisms which cause diseases
D. All of these

Answer

To solve the question "Open drain system is a breeding place for which of the following?" we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Open Drains**:
- Open drains are channels that carry wastewater and sewage from homes, industries, and factories. They are often not covered and can accumulate waste and stagnant water.

2. **Identifying Breeding Conditions**:
- Open drains create unhygienic conditions. They can become stagnant, especially during rainy seasons, leading to the accumulation of dirty water.

3. **Recognizing Breeding Organisms**:
- The stagnant and dirty water in open drains provides an ideal environment for various organisms to breed. Common organisms that thrive in such conditions include:
- **Flies**: They are attracted to decaying organic matter and waste.
- **Mosquitoes**: They lay their eggs in stagnant water, making open drains a perfect breeding ground.
- **Disease-causing organisms**: These include bacteria and viruses that can cause diseases like typhoid and cholera, which thrive in unsanitary conditions.

4. **Evaluating the Options**:
- Option A: Flies - Correct, as they breed in waste.
- Option B: Mosquitoes - Correct, as they breed in stagnant water.
- Option C: Disease-causing organisms - Correct, as they thrive in unhygienic environments.
- Option D: All of these - This option includes all the above organisms.

5. **Conclusion**:
- Since open drains can be breeding places for flies, mosquitoes, and disease-causing organisms, the correct answer is **Option D: All of these**.

### Final Answer:
**Option D: All of these**

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