To develop the main points for a speech on a question of value, you should ask a. "How do you know?"
b. "Why is this good or bad?"
c. "Why is_true?"
d. "How is this better than what we have now?"

B. "Why is this good or bad?"

Explanation:

You are trying to prove the value of the main points and therefore you should elaborate on whether or not the main points are good or bad for the overall topic.

i believe the answer is c