题目

（本小题满分14分）在一次抗洪抢险中，准备用射击的方法引爆从河上游漂流而下的一只巨大汽油罐。已知只有5发子弹备用，且首次命中只能使汽油流出，再次命中才能引爆成功．每次射击命中的概率都是，每次命中与否互相独立。     (I)求恰好射击5次引爆油罐的概率；        (II)如果引爆或子弹打光则停止射击，设射击次数为，求的分布列及的数学期望。I still remember the day I was driving to the supermarket I own. When I came out, I found a boy 31 my car with a brush. I went over and patted (拍) him on the shoulder, which surprised him very much. In no time he began to 　32 at me, so I was sure he 　33 some money. From the shoes he was wearing I could hardly imagine how poor he was. So I offered him a $100 bill. To my great surprise, he 　 34 to take it. When I was wondering what he was doing, he said, “I was waiting here for 4 hours, waiting for you. Your 　35 is so beautiful and I like it, but I don’t need that.” I knew he was mentioning the 　36 . As he had refused the money, I offered to drive him around the town. The boy became so 　37 that he got into the car at once, “Would you please drive me 　38 ? It is only about 3 miles.” What the boy wanted to do was to show off to his friends and his family. 　 　39 I stopped, he jumped out and ran into an old building, telling me to wait there for some time. Very soon he came out, saying to a little girl on his back, “Look at this beautiful car. I will buy you one some day.” I noticed his sister had a pale (苍白的) face. 　40 , her legs were too thin, and she was unable to 41 . After that day I went to his home several times. And I got to know more about him and his 　42 . Poor as they were, the boy once again refused my money, and said, “I can 　43 money by myself, thank you.” Soon I 　44 my manager of the supermarket that a boy would go to 　45 here the next day. No matter how poor we are, we would never give in to ourselves. 31. A. repairing B. cleaning C. fixing D. hitting 32. A. shout B. cry C. smile D. throw 33. A. lost B. got C. received D. needed 34. A. begged B. agreed C. allowed D. refused 35. A. car B. shoes C. suitcase D. clothes 36. A. box B. wheel C. paper D. bill 37. A. unhappy B. scared C. excited D. unfriendly 38. A. yard B. office C. school D. home 39. A. As soon as B. As long as C. As well as D. So far as 40. A. So B. However C. What’s worse D. In general 41. A. run B. jump C. climb D. walk 42. A. brother B. family C. friend D. boss 43. A. spend B. save C. make D. borrow 44. A. told B. asked C. answered D. warned 45. A. shop B. work C. sleep D. buy