The correct option is B Plasmid
A plasmid is an independent, circular, self-replicating DNA molecule that carries a few genes. During gene cloning, plasmid is described as a vector and used as a genetic taxi to deliver genes of interest to other unrelated organisms. The gene is inserted into a host cell, usually by way of a plasmid. There are a number of techniques used by genetic engineers to transfer DNA. The vector transfer takes advantage of natural processes that bacteria and viruses use to transfer their DNA, and it involves placing a gene into a gene taxi that takes the gene into the host cell.