完成一件工作，需要甲干5 天、乙6干天，或者甲干 7天、乙干 2天.问：甲、乙单独干这件工作各需多少天?
In 1834, the clock tower in London was burned down. People planned to buil d a new clock which would be the biggest and the best in the world. So the clock had to be big and keep very good time. Several years later the tower was finished. The people put the big clock in the tower, and made it ring out for the first time on July 11, 1859.
In order to give the big clock a good name, people held a meeting. Someone wanted to call it the Queen of Bells , and someone thought Victoria was good . At last, a man named Benjamin Hall stood up. He was a big man. Before he started to speak, someone shouted, "Why not call it Big Ben?" Everybody laughed and agreed with him.
From then on, Big Ben became its name. And it also became a famous building of London. People all over the world write to Big Ben. They even send bottles of oil to help keep Big Ben running. Big Ben is not only a clock but also a dear friend of people.
( ) 46. Big Ben's birthday is __________.
A. July 11, 1854 B. July 11, 1834
C. July 11 1859 D. July 11, 1852
( ) 47. How did Big Ben get its name?
A.Benjamin Hall gave it the name.
B.Big Ben got its name because of a joke.
C.Big Ben got its name from the Queen of the UK
D.Victoria gave it the name.
( ) 48. "Keep very good time" means ___________
A.have a good time
B.show people the correct time.
D.be made in time
( ) 49. Which of the following is NOT true?
A.People all over the world look upon Big Ben as their friends.
B.People all over the world even send oil to Big Ben.
C.People think Big Ben will reply their letters.
D.People think Big Ben is the biggest and the best clock in the world.
( ) 50. Benjamin Hall is ___________.
A. a man who built Big Ben
B. a man who was always very funny
C.the man who burnt down the old clock
D.a man who attended the meeting which was held to make a name for the big clock。