Which of the Following Mechanisms Is (Are)used to Coordinately Control

Which of the following mechanisms is (are) used to coordinately control the expression of multiple, related genes in eukaryotic cells?

A) organization of the genes into clusters, with local chromatin structures influencing the expression of all the genes at once
B) each of the genes sharing a common control element, allowing several activators to turn on their transcription, regardless of their location in the genome
C) organizing the genes into large operons, allowing them to be transcribed as a single unit
D) a single repressor able to turn off several related genes
E) environmental signals that enter the cell and bind directly to their promoters