50. .It is human beings who should be responsible _______ the harm done ____nature.

　 　 A. to, to　 　　　　　 B. for, to　 　　　　　　　　 C. for, at　 　　　　　 D. at, to

49. To keep the air clean, this hospital ______ all the patients _______ in and around it.

A. allows, smoking　　　 　　　　　　　　　　　 B. forbids, smoke　　

C. prevents, smoke 　　　　　　　　　　　　　　 D. prohibits, smoking

48. To tell you the truth, I think it is you,______ Mr. Black,______.

A. less than, which are to be blamed　　　　　　 B. rather than, that are to blame

C. other than, that is to blame　　　　　　　　　　 D. more than, who is to blame

47. It is required that the students _______ mobile phones in their school, so seldom ______ them using one.

A. shouldn’t be used; will you see　　　　　　　　　　　 B. not use; will you see　

C. don’t use; will you see　　　　　　 　　 　　　 D. shan’t use; you will see

46. Almost nobody can stand _______fun of before a crowd of people.

A. to be made　 　 B. to make　　 　　　　　　 C. being made　　 D. making

45. He felt guilty about losing ,and bad about__________ football as you are.

A. being as gifted at　　　　　 B. being so gifted for

C. not being as gifted at　　　　 D. not being so gifted for