Lac Operon will be turned on when

The correct option is "Lactose in more than glucose".

Step-by-Step Explanation:

The lac operon is an inducible operon system in bacteria (such as Escherichia coli) that regulates the transport and metabolism of lactose. Under normal conditions, bacteria prefer to use glucose as their primary carbon and energy source because it is more easily metabolized. Therefore, the activity of the lac operon is tightly controlled by the relative availability of both glucose and lactose in the cell's environment.

For the lac operon to be turned on (highly expressed), two conditions must be met:
1. Lactose must be present: When lactose is present, it is converted into allolactose, which acts as an inducer. Allolactose binds to the lac repressor protein, changing its shape and preventing it from binding to the operator site. This removes the physical roadblock to transcription.
2. Glucose must be depleted/low: When glucose levels are low, the cell produces cyclic AMP (cAMP). cAMP binds to the Catabolite Activator Protein (CAP), and this active cAMP-CAP complex binds to the promoter region to recruit RNA polymerase, facilitating high levels of transcription. If glucose is high, cAMP levels are low, and transcription remains very low even if lactose is present.

Thus, the lac operon is maximally activated and turned on when lactose is abundant (to induce the operon) and glucose is scarce. This is represented by the condition where lactose is more than glucose in the medium.