21.------- I didn’t pass the English exam last week .
-------- oh, you didn’t listen to your teacher and you _______ hard at your lessons.
A. should study B. should have studied C. shouldn’t have studied D. must have studied
22.Some students have trouble _____ maths while others have great difficulty _____ English words.
A. in , learn B. for , learn C. on , remembering D. with , remembering
