问题
选择题
—Why was he unhappy yesterday?
—A letter from home ______ an attack of homesickness.
A．set off
B．set out
C．set about
D．set up
答案
答案：A
考查短语辨析。set off爆发，set out出发，set about着手做，set up 建立，句意：昨天他为什么不高兴？一封来自家乡的信使他突发了思乡病。所以选A。