Isopropyl β-d-1- thiogalactopyranoside (IPTG),a lactose analog,acts as an inducer of the lac operon.What is its mode of action?

A)It functions as a co-activator of gene expression.
B)It inactivates the LacI repressor protein.
C)It activates the enzyme β-galactosidase.
D)It binds the RNAP for enhanced binding to the promoter.
E)It binds to the operator to enhance transcription initiation.