Answer:
The correct answer will be option-A
Step-by-step explanation:
An operon is a group of genes arranged in series having a single promoter which gets activated by the same stimuli which together controls the specific action. The operons are common in prokaryotic bacteria which could be inducible operons or repressible operons.
The repressible operons are the operons which remain activated all the time in a bacteria but can be repressed or stop when a molecule binds the operator. The co-repressor molecule is usually the product of the operon like the tryptophan in the trp operon which binds the protein and switches off the operon.
Thus, option-A is the correct answer.