a) The enhancer site is a distal control site many nucleotides upstream from the promoter site, and activates the initiation complex of transcription.
Explanation:
Enhancers are the regulatory DNA sequences that are generally located quite away from the coding regions of a gene. These sequences are mostly present upstream of promoter sequences. Enhancers regulate the gene expression by stimulating the formation of an active transcription initiation complex and thereby, increase the rate of RNA synthesis. Enhancers also serve as the binding site for specific regulatory proteins. These proteins bound to the enhancers then activate transcription by interacting with the proteins bound to the promoters.
