The correct option is D Single-stranded
A plasmid is a small, double-stranded, circular piece of DNA naturally found in many types of bacteria. Sometimes referred to as vectors, constructs, or clones, plasmids can be replicated independently from the bacterial genome and often encode genes that give bacteria specific traits. These traits can include the ability to resist treatment with an antibiotic the ability to kill other bacteria, and the ability to transfer the plasmid to other bacteria.