positive repressible regulatory mechanism, transcription of the structural gene (s) occurs in a. the absence or presence of the co-repressor b. the absence of the inducer, but not in its presence

B - the absence of the inducer, but not in its presence

Explanation:

In positive repressible regulalor mechanisms transcription of the structural gene (s) occurs in the absence of the inducer because proteins are normally bound to the pertinent DNA segment. when an inhibitor is bound by the inducer, it is prevented from binding the DNA. which will the stops the activation and transcription of the structural genes.

Example of positive repressible regulator is Activator.

Regulating the rate of transcription is a mechanism of gene regulation leading to the productionn of more than one protein product from a single gene.