Select the mismatched pair.

Options

A. Pseudomonas - Denitrifying bacteria
B. Rhizopus - Bread mould
C. Rhizobium - Used for making idli and dosa
D. Nitrosomonas - Nitrifying bacteria

Explanation

To solve the question of selecting the mismatched pair, we will analyze each option provided:

1. **Pseudo-monus denitrifying bacteria**: This option states that Pseudomonas is a denitrifying bacterium. This is correct because Pseudomonas species are known to convert nitrates into nitrogen gas, thus playing a role in the nitrogen cycle.

2. **Rhizopus in bread mode**: This option refers to Rhizopus, which is indeed a type of mold commonly found in bread. This is also correct, as Rhizopus is known for causing bread to mold.

3. **Rhizobium used for making idli and dosa**: This option claims that Rhizobium is used in making idli and dosa. This is incorrect. Rhizobium is a bacterium that lives in the root nodules of leguminous plants and is involved in nitrogen fixation. Idli and dosa are made using fermented rice and lentils, typically involving yeast or other fermentation processes, not Rhizobium.

4. **Nitrifying bacteria**: This option states that nitrifying bacteria are involved in the nitrogen cycle, converting ammonia into nitrates. This is correct.

Now, we can summarize our findings:

- The first option is correct.
- The second option is correct.
- The third option is incorrect (mismatched).
- The fourth option is correct.

Thus, the mismatched pair is **Rhizobium used for making idli and dosa**.

### Final Answer:
The mismatched pair is: **Rhizobium used for making idli and dosa**.

---