问题补充：
— 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
答案：
A. took up
(答案→)B. set off
C. brought in
D. built up
解析：A. took up占据B. set off引起，出发C. brought in 带来D. built up逐渐建立；句意：约翰怎么了？他在那里做了好几个小时了.一封来自他父亲的明信片使他想家了。故选B
