Which of the following group of words can be correctly identified with Rhizobium?

Options

A. Roots of legumes, parasite, soluble nitrogen compounds
B. Leguminous plants, symbiotic, stem nodes
C. Root nodules, pitcher plant, nitrogen deficient soil
D. Nitrogen-fixation, root nodules, leguminous plants

Explanation

To identify the correct group of words associated with Rhizobium, we can analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Rhizobium**:
- Rhizobium is a type of bacteria that plays a crucial role in the nitrogen cycle. It is known for its ability to convert atmospheric nitrogen into a form that plants can use, specifically soluble nitrogen compounds.

2. **Analyzing the Options**:
- **Option 1**: Roots of legumes, parasite, soluble nitrogen compound
- While Rhizobium is associated with the roots of legumes and does produce soluble nitrogen compounds, it is not a parasite. This option is incorrect.

- **Option 2**: Leguminous plant, symbiotic, stem nodes
- Rhizobium does form a symbiotic relationship with leguminous plants, but it is not found in stem nodes. This option is also incorrect.

- **Option 3**: Root nodules, pitcher plant, nitrogen deficient soil
- Rhizobium is indeed found in root nodules of leguminous plants, but it is not associated with pitcher plants, which are carnivorous. This option is incorrect.

- **Option 4**: Nitrogen fixation, root nodules, leguminous plant
- This option correctly identifies Rhizobium's role in nitrogen fixation, its presence in root nodules, and its association with leguminous plants. This option is correct.

3. **Conclusion**:
- The correct answer is **Option 4: Nitrogen fixation, root nodules, leguminous plant**.

### Final Answer:
The group of words that can be correctly identified with Rhizobium is **Nitrogen fixation, root nodules, leguminous plant**.