Which of the following BEST describes catabolite repression of the lac operon?

A) The operon is transcriptionally inactive in the absence of lactose.
B) The operon is transcriptionally inactivated by a repressor protein, which binds to glucose.
C) The operon is transcriptionally active when an activator protein binds to the promoter in the absence of glucose.
D) Glucose is the preferred energy source for E. coli.
E) The operon is repressed by its protein products.