6. She concentrated ______ studying for the exam.
A. in B. for C. with D. on
7. He was always ready to help others, ______ , he was like by everyone.
A. in turn B. in store C. in return D. by turns
8．------What would you do if it ______ tomorrow?
------We have to carry it on, since we’ve got everything ready.
A. rain B. rains C. will rain D. is raining
