Ans. (A). plasmid.
Plasmid can be defined as an extra-chromosomal, circular, and self-replicating DNA molecule, commonly found in bacteria (prokaryotes). Plasmids provide several advantages to the bacteria, such as gene transfer and antibiotic resistance. Cell membrane, cytoplasm, and flagellum are often found in both prokaryotic and eukaryotic cells. Plasmids are rarely found in eukaryotic cells.
Thus, the correct answer is option (A).