In a group discussion which is most clearly a clarifying question

In a group discussion, which is most clearly a question that keeps the discussion moving? A. what did Emily mean by "people fussed over her"? B. Han, what did you think after hearing Emily's reasons? C. How much time do we have left to discuss the book? D. Is that an example of the book or the movie? If so, the answer would most probably be letter B. If the question on letter B will be answered by one of the members of the group, it would keep the discussion moving since the group leader can enumerate the reasons of Emily and distribute the question among the members of the group.