题目

— Why was our foreign teacher unhappy yesterday?— News about the tsunami striking her country ______ an attack of homesickness.A. set for B. set outC. set about D. set off 答案：【答案】D【解析】试题分析：考查短语。句意：为什么我们的外教今天不开心？海啸袭击她的国家的新闻引发了她的思乡之情。A. set for安排；B. set out出发，开始；C. set about着手，开始；D. set off引发；根据词义可知是引发了思乡之情，故选D项。若实数x，y满足|x＋y|＝4，则xy的最大值是________．