In case of lac operon when disaccharide enters the cell :

Options

A. it binds to the bound repressor to the operator and the structural genes are transcribed because the RNA polymerase can recognise and bind the transcription initiation site
B. it binds to the repressor and structural genes are transcribed because the repressor has an altered conformation, is inactivated and does not bind the operator
C. the membrane protein interacts with the operator and the RNA polymerase can recognise the transcription initiation site
D. the membrane protein has an altered conformation and does not interact with the operator, thus leading to the trasncription of the structural genes.

Answer

B