Methanogens are commonly found in

Options

A. anaerobic sludge.
B. rumen of cattle.
C. gobar.
D. all of these .

Answer

**Step-by-Step Solution:**

1. **Understanding Methanogens:**
- Methanogens are a type of archaea that produce methane as a metabolic by-product in anoxic conditions. They are anaerobic microorganisms.

2. **Analyzing the Options:**
- The question asks where methanogens are commonly found. We will evaluate each option provided.

3. **Option 1: Anaerobic Sludge**
- Anaerobic sludge is a mixture of microorganisms that treat wastewater in the absence of oxygen. Methanogens thrive in this environment as they help in breaking down organic matter and produce methane.
- **Conclusion:** This option is correct.

4. **Option 2: Rumen of Cattle**
- The rumen is a part of the digestive system in cattle where fermentation occurs. Methanogens are indeed present in the rumen, aiding in the digestion of cellulose and producing methane as a by-product.
- **Conclusion:** This option is also correct.

5. **Option 3: Cow Dung**
- Cow dung is rich in organic matter and provides an anaerobic environment where methanogens can thrive. They are present in cow dung and contribute to methane production during decomposition.
- **Conclusion:** This option is also correct.

6. **Option 4: All of the Above**
- Since options 1, 2, and 3 are all correct regarding the presence of methanogens, option 4, which states "all of the above," is also correct.

7. **Final Answer:**
- The correct answer is option 4: "All of the above," as methanogens are commonly found in anaerobic sludge, the rumen of cattle, and cow dung.

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