A foreign language like English is difficult to learn so you work too hard.A. can’tB. mu

问题补充：

A foreign language like English is difficult to learn, so you work too hard.

A. can’t

B. must

C. shouldn’t

D. ought to

答案：

(答案→)A. can’t

B. must

C. shouldn’t

D. ought to

解析：考查情态动词：can’t/couldn’t….too….,在…也不为过，其他情态动词没有这个用法，句意：向英语这样的外语很难学，所以你再努力也不为过。选A。