In the lac operon of E. coli, what happens when lactose is present but glucose levels are low?

The lac repressor binds to the operator, preventing transcription.

cAMP levels decrease, leading to reduced binding of CAP-cAMP to the promoter.

cAMP levels increase, enhancing the binding of CAP-cAMP to the promoter and facilitating transcription.

The lac operon is permanently deactivated, and no transcription occurs.