23．(2011黑龙江哈九中高三上学期期末考试) There’s no light on in the dormitory．They must have gone to attend the concert to be held on the campus，______
A. didn’t they? B. mustn’t they? C. haven’t they？ D. shouldn’t they?
24. (2011贵州省五校第四次联考) When asked the reason for moving to the USA，he said, “Soccer is huge around the world apart from America， so that’s _________ I want to make a difference.”
A. where B. why C. what D. how
