Lactose digestion in E. coli begins with its hydrolysis by the enzyme \(\beta\)-galactosidase. The gene encoding \(\beta\)-galactosidase, lacZ, is part of a coordinately regulated operon containing other genes required for lactose utilization.

Which of the following figures correctly depicts the interactions at the lac operon when lactose is NOT being utilized? (The legend below defines the shapes of the molecules illustrated in the options.)

The question asks for a figure which shows the interactions when lactose is not being utilized. Since lactose is present in the first two options, we can rule these two out.

When lactose is not being utilized, we would not expect any need for the enzyme \(\beta\)-galactosidase, which is encoded by lacZ. Transcription should therefore not proceed. The repressor protein prevents transcription.