Many websites have been to help people study foreign languages.
A. set off
B. set up
C. set down
D. set out
网友回答
A. set off
(答案→)B. set up
C. set down
D. set out
解析：考查动词短语：A. set off出发，引发，引爆，B. set up建立，C. set down 记下， D. set out出发，句意是：很多网站被建立为了帮助学习外语的人。选B。