Answer:
The correct answers are option A. "Maltose removes a repressor from an operon with an efficient promoter" and option C. "Maltose causes an activator to bind an operon with an inefficient promoter".
Explanation:
Two ways at which maltose operon works in the presence of maltose is by maltose removing a repressor from an operon with an efficient promoter and by maltose causing activator to bind an operon with an inefficient promoter. Maltose removes the repressor malR (Maltose operon transcriptional repressor) with an efficient promoter called malE. Additionally, maltose causes an activator to bind an operon with an inefficient promoter known as malT.