53.It was ____ then that I came to know that knowledge comes from practice.

　　A) until C) till

　　B) not until D) since

　　54.The world's supplies of petroleum ____.

　　A) have been gradually being exhausted

　　B) have gradually exhausted

　　C) are gradually exhausted

　　D) are being gradually exhausted

　　55.Everything depends on ____ we have enough time.

　　A) if C) whether

　　B) when D) that

　　56.I'd just as soon ____ rudely to her.

　　A) you not speak C) you didn't speak

　　B) your not speaking D) you hadn't spoken

　　57.The concert was so interesting that we all felt it ended ____ soon.

　　A) but too C) very

　　B) only too D) too

　　58.The roar of the crowd finally ____ to a murmur.

　　A) reduced C) decreased

　　B) diminished D) cut down

　　59.It's very discourteous to ____ during some one's conversation.

　　A) inspect C) interfere

　　B) interrupt D) instruct

　　60.Sometimes even the smallest thing will upset an ____ person.

　　A) annoyed C) irritable

　　B) irritated D) angry

　　61.The conversation was so interesting that we were ____ of the lateness of the hour.

　　A) negligible C) irrelevant

　　B) inattentive D) oblivious

　　62.The rainbow is one of the most beautiful ____ in nature.

　　A) phenomenon C) appearance

　　B) phenomena D) experience

　　63.It is ____ that nowadays fiber is considered to be an important part of a healthy diet.

　　A) serious C) significant

　　B) great D) vital

　　64.The performance will begin ____ at eight?thirty.

　　A) precisely C) accordingly

　　B) consequently D) exceedingly

　　65.Mr.Smith, a chemistry teacher, never stops ____ new and better ways to improve his teaching.

　　A) discovering C) searching for

　　B) looking for D) finding out

　　66.People greatly differ ____ their views of life.

　　A) from C) at

　　B) to D) in

　　67.The geographical location of Hubei is quite favorable for agricultural production. It's ____ the land of fish and rice.

　　A) famous for C) known as

　　B) known by D) known to