Answer:
The correct answer will be option-C.
Step-by-step explanation:
The RNA polymerase is the enzyme which synthesizes the mRNA molecules using a single strand of DNA. RNA polymerase has the ability to bind nucleotide at 3' end of the strand thus proceeding the strand in 5' to 3' direction.
In the given question, gene expression of the insulin-producing gene has been discussed which uses transcription factors. The transcription factors assist RNA polymerase enzyme to attach to the promoter sequence and start synthesizing RNA molecule.
Thus, Option-C is the correct answer.