He is only too ready to help others, seldom, ______, refusing then they turn to him for help.
Would you be kind enough to help the boy _____ Chinese is really hard to learn?
_____ in the library regulations that any book borrowed be returned by due time, or the borrower will be fined.
—How did you like the concert last night ?—I enjoyed it very much, but the dancers _____ a better job.
I appreciate _____ the opportunity to work in your company two years ago.
_____ economic, political and cultural differences, it is difficult for China and America to fully understand each other.