Glucose increases cAMP levels, which activates CAP, enhancing lac operon transcription.

Glucose decreases cAMP levels, reducing CAP binding to the promoter, thus inhibiting lac operon activation.

Glucose prevents lactose from binding to the lac repressor, ensuring the operon is always repressed.

Glucose has no effect on cAMP levels, but instead directly inhibits RNA polymerase binding to the promoter.