The commonest vector of plague is:: (A) Xenopsylla cheopis, (B) Musca domestica, (C) Xenopsylla astia, (D) Pulex irritans
Answer is A. Xenopsylla cheopis is the commonest and the most efficient vector of plague. Other vectors include Xenopsylla astia, Xenopsylla brasiliensis and Pulex irritans. Ref: Park 21st edition: page 268.