Which of the following is a correctly matched pair of useful microorganisms and their activities?
`{:(" Microorganism", " Activity"), (I. "Yeast", "Ferments glucose to"),(,"produce alcohol"),(II. "Bacteria","Decompose dead materials"),( III. "Nitrogen-fixing", "Convert nitrogen"), (" bacteria","into protein in plants"):}`

Options

A. I only
B. I and II
C. II and III
D. I, II and III

Explanation

To determine the correctly matched pair of useful microorganisms and their activities, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze Yeast:**
- Yeast is a unicellular fungus.
- It ferments glucose to produce alcohol.
- This statement is correct.

2. **Analyze Bacteria:**
- Bacteria are known to decompose dead materials.
- They act as decomposers by breaking down dead organic matter and returning nutrients to the soil.
- This statement is also correct.

3. **Analyze Nitrogen-fixing Bacteria:**
- Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia.
- This ammonia can then be utilized by plants, but they do not convert nitrogen directly into proteins.
- Therefore, this statement is incorrect.

4. **Conclusion:**
- The first pair (Yeast - Ferments glucose to produce alcohol) is correct.
- The second pair (Bacteria - Decompose dead materials) is also correct.
- The third pair (Nitrogen-fixing bacteria - Convert nitrogen into protein in plants) is incorrect.
- Thus, the correctly matched pairs are the first and second options.

### Final Answer:
The correctly matched pairs of useful microorganisms and their activities are:
- Yeast - Ferments glucose to produce alcohol
- Bacteria - Decompose dead materials