Answer
b.
Work Step by Step
Option a. is incorrect. The promoter is a region on the DNA molecule where RNA polymerase binds to start the process of transcription.
Option c. is incorrect. An intron is a portion of the mRNA that does not code for a protein and is cut out of the transcribed mRNA to produce a final mRNA strand that will be used to make the protein.
Option d. is incorrect. An allele is a form of a gene.
Option b. is correct. An operon is a group of genes that are usually translated together because the proteins they code for have related functions.