Final answer:
The CI protein stabilizes the lysogenic state and represses the expression of Cro protein.
Step-by-step explanation:
The correct answer is B) Lysogenic; Cro. In bacteriophage lambda, the CI protein stabilizes the lysogenic state by binding to specific DNA sequences and repressing the expression of Cro protein. The Cro protein, when expressed, promotes the switch from the lysogenic cycle to the lytic cycle. Therefore, CI prevents the lytic cycle and promotes the maintenance of the lysogenic state.