39. The eukaryotic transcription factor CREB is active when it is phosphorylated and it binds cAMP response elements (CREs) in the promoters of genes, activating transcription. The mechanism of transcription activation is best described by the following statements. (A) CREB binds the CREs and recruits a complex of proteins that acetylates histones in nucleosomes at the promoter; thereby displacing nucleosomes and facilitating the assembly of basal transcription factors on the promoter. (B) CREB binds the CREs and recruits nucleosome assembly proteins that increase the amount of DNA assembled into nucleosomes in the promotere; thereby increasing the rate of basal transcription factor binding. (C) CREB binds to the CREs and prevents the repressor form binding; thereby increasing the rate of basal transcription factor binding. (D) CREB binds the CREs and directly recruits the basal transcription factors to bind the promoter.