Which of the Following Statements Most Accurately Describes General Features

Which of the following statements most accurately describes general features of inducible and repressible systems for the negative control of transcription of an operon?

A) Repressor protein is bound to the operator region in the absence of small effector molecules in both inducible and repressible systems.
B) Repressor protein does not bind to the operator region when specific small effector molecules bind to the repressor protein in both inducible and repressible systems.
C) Repressor protein binds to the operator in repressible systems only after binding co-repressor, whereas repressor protein from inducible systems binds to operator only in the absence of an inducer.
D) Inducers are end products of the biosynthetic sequence which they control, whereas co-repressors are substrates for the catabolic metabolic pathways that they control.
E) Inducible systems in prokaryotes are generally positively controlled at the transcriptional level, whereas repressible systems are negatively controlled at the transcriptional level.