_____the film so many times , I don’t need to see or hear it___what is happening now on the screen .

    Before you go to another country it is a great help if you know the language and some of the customs of the country.
    When people meet each other for the first time in Britain, they say “How do you do?” and shake hands. Usually they do not shake hands when they just meet or say goodbye. But they shake hands after they haven't met for a long time or when they will be away from each other for a long time.
    Last year a group of German students went to England for a holiday. Their teacher told them that the English people hardly shake hands. So when they met their English friends at the station, they kept their hands behind their backs. The English students had learned that the Germans shake hands as often as possible, so they put their hands in front and got ready to shake hands with them. It made both of them laugh.

阅读理解

    Helen got up at seven thirty. Her parents and her little twin brothers went travelling in Australia and she had to take care of herself at home. She opened the fridge, but she found only three pieces of bread in it. She decided to have breakfast in the restaurant at the other side of the street. She sat at a table and the waitress came up to her and said, “Can I take your order, Helen?”

    “But you didn't show your menu to me, Miss White,” said the girl.

    “Oh, sorry! I forget it. Here it is.”

    Helen looked at the menu carefully. It was:

bread  $1.5          egg  $ 0.4

pizza  $2.5          cola  $ 0.3

sandwich $1.5        milk  $ 0.6

hamburger $2.5       coffee  $ 0.9

    Helen took out her purse and found there was only 7 dollars in it.

    “Well,” said White.“What about a hamburger, a pizza, two eggs and a glass of cola?”

    “Oh, no,” said the girl. “I'll buy a storybook this afternoon. It's 2 dollars.”

    “I see,” said the waitress. And then she brought the girl a nice breakfast.

已知y与x-1成反比，并且当x=3时，y=4，则y与x之间的函数关系是(    )

利用定积分的几何意义，计算： $\int {}_1^2\sqrt{4-x^2}dx$ ＝____.