How does glucose indirectly regulate the lac operon through its effect on cyclic AMP (cAMP) levels?

• A. Glucose increases cAMP levels, which activates CAP, enhancing lac operon transcription.
• B. Glucose decreases cAMP levels, reducing CAP binding to the promoter, thus inhibiting lac operon activation.
• C. Glucose prevents lactose from binding to the lac repressor, ensuring the operon is always repressed.
• D. Glucose has no effect on cAMP levels, but instead directly inhibits RNA polymerase binding to the promoter.

Answer: (B)