题目

已知等差数列满足。 （I）求数列的通项公式；    （II）求数列的前项和。 答案：A man was walking along the street when he saw a woman struggling with a large package（包裹）. It was half in and half out of her car.He was a kind of man so he went up to the woman and said, "Let me give you a hand with that package. It looks very .""That's very kind of you," the woman said. "I'm having a lot of with it. I think it's stuck.""Together we'll soon move it," the man said. "I'll get into the and take the other end.""Oh, that's very . Thank you so much," the woman said gratefully. He got into the back of the car and took hold of the other end of the package."Right," he said, "I'm ready." And he began to push with all his .For several minutes the man and the woman struggled with the package. Soon they were both red in face and out of ."Let's pause for a minute," the man said. "You're right. It really is ."They paused for a few to wipe the perspiration from their faces and get their breath back.Then the man said, "Let's try again. Are you ?"They took hold of the package again."One, two, three!" the man said, and again they their struggle with the package.At last, when they were both , the man said, "I'm sorry, but the package really seems to be stuck. I don't think there's any way we can get it out of the car.""Get it out of the car!" the woman cried. "You fool! I'm trying to get it in!"1.A. helpful B. careful C. useful D. hopeful2.A. big B. small C. heavy D. light3.A. problems B. trouble C. pain D. worry4.A. seat B. package C. street D. car5.A. sensible B. interesting C. possible D. moving6.A. car B. box C. seat D. chair7.A. power B. strength C. hands D. arms8.A. mind B. air C. exercise D. breath9.A. stuck B. taken C. shaken D. broken10.A. times B. hours C. moments D. days11.A. alright B. ready C. OK D. right12.A. both B. all C. each D. every13.A. stopped B. kept C. paused D. continued14.A. interested B. excited C. exhausted D. surprised15.A. mostly B. completely C. nearly D. greatly