The most important feature in a plasmid to be used as a vector is

Options

A. Origin of replication (Ori)
B. presence of a selectable marker
C. presence of sites for restriction endonuclease
D. its size

Explanation

### Step-by-Step Solution:

1. **Understanding the Role of Plasmids**: Plasmids are small, circular DNA molecules found in bacteria that can replicate independently of chromosomal DNA. They are commonly used as vectors in genetic engineering to transfer genetic material into host cells.

2. **Identifying Key Features of Plasmids**: Several features are essential for a plasmid to function effectively as a vector:
- **Origin of Replication (ORI)**: This is a specific DNA sequence that allows the plasmid to replicate within the host cell.
- **Selectable Marker**: This feature enables the identification of cells that have successfully taken up the plasmid.
- **Restriction Endonuclease Sites**: These are specific sequences where enzymes can cut the DNA, allowing for the insertion of foreign DNA.
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