In the Figure Below, Are the Genes That Encode the Enzymes

Multiple Choice

In the figure below, are the genes that encode the enzymes needed to make tryptophan on or off?

A) The genes are on because the genes involved in tryptophan production are housekeeping genes.
B) The genes are on because the complex of tryptophan and repressor protein allows RNA polymerase to bind to the promoter.
C) The genes are off because the complex of tryptophan and repressor protein prevents RNA polymerase from interacting with regulatory DNA.
D) The genes are off because when tryptophan is plentiful in the environment, RNA polymerase is not made.