An outer covering membrane is absent over

Options

A. nucleolus
B. lysosome
C. mitochondrion
D. plastids

Explanation

To solve the question "An outer covering membrane is absent over," we need to analyze the options provided: nucleolus, lysosome, mitochondrion, and plastid.

### Step-by-Step Solution:

1. **Understand the Options**:
- **Nucleolus**: A structure found within the nucleus of a cell.
- **Lysosome**: A membrane-bound organelle containing digestive enzymes.
- **Mitochondrion**: A membrane-bound organelle known as the powerhouse of the cell.
- **Plastid**: A membrane-bound organelle found in plant cells, involved in photosynthesis and storage.

2. **Identify Membrane Presence**:
- **Nucleolus**: It is a dense, spherical structure located inside the nucleus and does not have a surrounding membrane.
- **Lysosome**: Surrounded by a lipid bilayer membrane.
- **Mitochondrion**: Also has a double membrane structure.
- **Plastid**: Enclosed by a membrane.

3. **Conclusion**:
- Among the options, the only structure that does not have an outer covering membrane is the **nucleolus**.

### Final Answer:
The correct answer is **nucleolus**.

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