which of the following statements regarding transcriptional attenuation is true? choose one:a. transcriptional attenuation is important for the control of most catabolic operons.b. transcriptional attenuation is a form of rho-dependent transcriptional termination.c. transcriptional attenuation is used in place of, rather than in addition to, repressor control of an operon.d. transcriptional attenuation requires the presence of an operator sequence.e. transcriptional attenuation allows the cell to respond rapidly to fluctuating levels of metabolites (e.g., amino acids).