How Is Glucose Involved in the Catabolite Repression of the Lactose

How is glucose involved in the catabolite repression of the lactose operon?

A) It has nothing to do with regulation of the lactose operon.
B) It results in decreased cAMP levels, which in turn leads to decreased CRP binding; thus the lac operon is repressed even if lactose is present along with the glucose.
C) It is also a substrate for $\beta$ -galactosidase and thus competes with lactose for this enzyme.
D) Its presence in the cell increases the amount of lac repressor in the cell.