At the party, John made up a joke, people burst out laughing.A. on whichB. by whichC. at w

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A. on which
B. by which
(答案→)C. at which
D. from which
解析：本题考查定语从句。句中先行词为a joke，介词at表示“听到”之意，故用at which。句意：在晚会上John编了一个笑话，听到的人们大笑起来。