Question

Which of these is a common feature for the lac and trp operon? A. Regulatory proteins bind to operator B. Regulatory proteins bind to promoter C. Regulatory proteins bind to repressor

Answer 1

An operon consists of a repressor, promoter, operator, and any structural repressible and inducible systems.
The two systems are the lac and trp operon. In the trp operon, the regulatory proteins will bind to the repressor. This is known as a repressible system. In the lac operon, the regulatory proteins will simply interact with the repressor protein so that it cannot bind to the operator. This is known as an inducible system.
The answer is C. Regulatory proteins bind to repressor

Answer 2

 C. Regulatory proteins bind to repressor

Both produces certain proteins to break down lactose as a food source.