Bacteria Can Be Studied in the Laboratory by Growing Them

Bacteria can be studied in the laboratory by growing them on defined liquid or solid medium. A typical bacterial genome consists of a single circular chromosome that contains several million base pairs. Some bacterial genes may be present on plasmids, which are small, circular DNA molecules that replicate independently of the bacterial chromosome
-Which is true of plasmids?

A) They are composed of RNA.
B) They normally exist outside of bacterial cells.
C) They possess only a single strand of DNA.
D) They contain an origin of replication