One problem which arises in free discussions is that coordinating activities is difficult; one member may be talking about the problem, while another one is proposing a solution, and the other one may be analyzing the causes. However, using formal plan tell the members what they should thank and talk about at different stages of discussion. In fact, by using a formal plan, group members reach an agreement on the stages of discussion. So option B (The plan can help the group build a consensus and choose a course of action) is the answer.
