单选题 Nobody knew how to __________such a problem.

单选题 Although they were all worried about his safety，he insisted ______going there together with us.

单选题 I’ll ask Mr. Smith to ring you up _________he comes back to the office. 

单选题 The work will_________a lot of your energy.

单选题 They provide us ________a lot of food when we were in trouble.

单选题 She is a(n)__________secretary, so everybody likes her.

单选题 Nothing can _________his mind __________the book.

单选题 He could see nothing__________the top of the mountain.