Answer:
B. Summarize their positions in one sentence.
Explanation:
It is useful to summarize your position in one sentence before staring a debate. This has several advantages. Summarizing your argument in this way can help you get a clearer idea in your mind of what it is that you want to defend. Moreover, it can help you find a clear direction for you following arguments. Finally, it can help you find common ground with your opponent, or highlight your most important differences.
