题目内容：

how long have you lived in Germany?__for the past six years.
A.off and on B.on and up C.about D.at least

优质解答

A
on and up 没有这个说法
如果用about就应该直接跟时间,而不会中间加个for
at least,至少.道理同about
所以选off and on: adv.断断续续地