Why Is Binding of The $\lambda$ Phage CI Repressor to O_R1 and O_R2 Necessary for Transcription

Why is binding of the $\lambda$ phage cI repressor to O_R1 and O_R2 necessary for transcription from P_RM?

A) It facilitates binding of the RNA polymerase to P_RM.
B) It blocks transcription from P_L which competes for the RNA polymerase.
C) It prevents transcription of an antisense RNA.
D) It stabilizes the transcript from P_RM.
E) It allows read through a transcriptional terminator.