Methanogens grow anaerobically on cellulosic material and produce
A. methane
B. oxygen
C. carbon dioxide
D. hydrogen

Options

A. A,C,D
B. A,B,C,D
C. B,C,D
D. A,B

Answer

To solve the question regarding what methanogens produce when they grow anaerobically on cellulosic material, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Methanogens**: Methanogens are a group of microorganisms that produce methane as a metabolic byproduct in anoxic conditions (absence of oxygen). They are a type of archaea.

**Hint**: Remember that methanogens thrive in anaerobic environments, which is crucial for their metabolic processes.

2. **Anaerobic Conditions**: The question specifies that methanogens grow anaerobically. This means they do not require oxygen for their growth and instead rely on other substrates.

**Hint**: Think about what types of environments are anaerobic and how that affects microbial metabolism.

3. **Cellulosic Material**: Methanogens can utilize cellulosic materials, which are organic compounds made of cellulose. These materials are often found in plant matter.

**Hint**: Consider what types of organic materials are rich in cellulose and how they might be broken down by microorganisms.

4. **Metabolic Products**: When methanogens metabolize cellulosic material, they produce several gases. The primary product is methane (CH4), but they also produce carbon dioxide (CO2) and sometimes hydrogen (H2) as byproducts.

**Hint**: Recall the common gases produced during anaerobic digestion, especially in the context of methanogenesis.

5. **Eliminating Incorrect Options**: The question provides four options:
- A. Methane
- B. Oxygen
- C. Carbon dioxide
- D. Hydrogen

Since methanogens do not produce oxygen, we can eliminate option B. The remaining options (A, C, and D) are correct as they are all products of methanogen metabolism.

**Hint**: Focus on the metabolic pathways of methanogens to determine which products are expected.

6. **Final Answer**: Therefore, the correct answer is:
- A. Methane
- C. Carbon dioxide
- D. Hydrogen

### Summary of the Answer:
Methanogens grow anaerobically on cellulosic material and produce methane (A), carbon dioxide (C), and hydrogen (D). They do not produce oxygen (B).