How Is Lac Operon Transcription Regulated by the Presence or Absence

How is lac operon transcription regulated by the presence or absence of lactose? ​

A) When lactose is available, the repressor will bind to allolactose instead of blocking RNA polymerase.
B) When lactose is not available, the repressor will bind to the promoter and block RNA polymerase from binding to the promoter.
C) When lactose is not available, the repressor will bind to allolactose.
D) When lactose is available, allolactose is produced and binds to the operator, blocking RNA polymerase.
E) In the absence of lactose, transcription occurs at a low level resulting in the production of allolactose, which in turn stimulates the cell to take up lactose.