"Rickettsia" are

Options

A. Bacteria
B. Virus
C. PPLO
D. Micro organism

Answer

### Step-by-Step Solution

1. **Understanding Rickettsia**: Rickettsia are a type of bacteria. They are classified under the group of non-motile, gram-negative bacteria.

2. **Analyzing the Options**:
- **Option 1: Bacteria**: This is the correct answer. Rickettsia are indeed bacteria.
- **Option 2: Virus**: This option is incorrect. Viruses are different from bacteria as they require a host cell to replicate and do not have cellular structures like bacteria.
- **Option 3: PPLO (Pleuropneumonia-like Organisms)**: This refers to mycoplasma, which are bacteria that lack a cell wall. While Rickettsia are also bacteria, they are not classified as mycoplasma.
- **Option 4: Microorganism**: This term is too broad as it includes bacteria, viruses, fungi, and other microscopic organisms. Therefore, this option is not specific enough to describe Rickettsia.

3. **Conclusion**: Based on the analysis of the options, the correct classification for Rickettsia is that they are bacteria.

### Final Answer
Rickettsia are **bacteria**.