—What's the matter with John? He has been sitting there for hours．
—A postcard from his father an attack of home - sickness in him．
A. took up
B. set off
C. brought in
D. built up
网友回答
A. took up
(答案→)B. set off
C. brought in
D. built up
解析：考查词组辨析：A.拿起B.出发，引起，使爆炸C.带来，引进D.逐渐获得。本句的意思是;--约翰怎么了？--他坐在那里几个小时了。---父亲寄来的明信片使他想家”。故选B.