21. The λ repressor encoded by the cI gene can act as a repressor or an activator. How does the λ repressor act as an activator to stimulate transcription of the cI gene? (A) It binds to OR2 and contacts RNA polymerase at PRM to stimulate transcription. (B) It binds to OR3 and contacts RNA polymerase at PR to stimulate transcription. (C) It binds to OL2 and contacts RNA polymerase at PLM to stimulate transcription. (D) It binds to OL3 and contacts RNA polymerase at PL to stimulate transcription. (E) It binds to ORE and contacts RNA polymerase at PRE to stimulate transcription.