C. To clearly state the main idea of the paragraph
B an earth quke or unpredicted scale
True. If the audience is slow to respond to your question, you should answer it yourself rather than let there be silence. When speaking in public, these questions are considered rhetorical and doesn't really need to be answered, this should be part of your speaking script. This stirs the audience, but then you need to answer it yourself to transition to another point.
