The correct option is B It consists of a promoter, operator and structural genes
Operons generally occur in prokaryotes. An operon is a part of the genetic material (or DNA) which is a co-ordinated group of genes that act as a single regulatory unit having one or more structural genes, an operator gene and a promoter gene. The operon is usually regulated by a regulatory gene which codes for the repressor protein, which, in turn, plays a major role in switching the operon on and off.