题目

如图1-5-8,在△ABC中,∠ACB=90°,CD⊥AB,垂足为D,AC=12,BC=5,则CD的长为(    )图1-5-8A.           B.              C.                D. 答案：解析：AB=.∵AD·AB=AC2,BD·AB=BC2,∴AD=,BD=.又CD2=AD·BD,∴CD==.答案:A    Mrs. Smith has two children now. She tries to keep thin and never eats any meat or eggs. She likes all kinds of nice clothes. Mr. Smith has to spend much money on them. But the man always wears old clothes. He has not enough money to buy new clothes. Mrs. Smith hopes to keep young. She doesn’t want others to know how old she is. It was snowing heavily one afternoon. The head of her office went to a meeting. The woman had nothing to do. So she began to tell Mr. Smith about her birthday party. Mr. Smith works in the same office.   “You should have seen the cake ,” said the woman. “It was nice and delicious!I put nineteen candles on it一one for a year!”“Was it possible?” asked Mr. Smith. “ You couldn’t bum at both ends at all!”6. There are people in Mrs. Smith's family.   A. two   B. three   C. four   D. five7. Mrs. Smith hopes to be .   A. healthy and strong   B. beautiful and young   C. friendly and free   D. busy and clever8. Mr. Smith wears old clothes because .   A. he works in a factory   B. he is a farmer   C. he has a lot of housework to do at home   D. he has not enough money to buy new ones for himself9. Mrs. Smith told Mr. Smith about her birthday- party.   A. after the head left the office   B. when it began to snow   C. on her way home   D. when she met him in the street10. From the story we know that.   A. Mrs. Smith was young   B. Mrs. Smith looked poor   C. Mrs. Smith was thirty-eight   D. the woman was telling the truth about her age