题目

将气球吹大，用细绳把出口扎紧，用浸透酒精的棉花擦拭气球，然后给气球扇风或迎风摆动气球，会观察到气球的体积明显缩小，请用物理知识解释． 答案：          答：用浸透酒精的棉球擦拭扎紧的气球，然后摆动气球或給气球扇风，会增大酒精上方空气流动的速度，从而使酒精的蒸发加快，而蒸发需要从周围吸热，使气球内空气的温度降低，密度变大，导致气球的体积缩小．I have returned to my hometown after I was away ten years ago. So many things have changed around here. It has become better and better. When I left here, there was a small pool on the right of my house. Now the pool has gone and people have built a large shopping mall(商场) there.The biggest changes have taken place in the center of the city. There are sidewalks on both sides of the street. You can see a street center with so many tall buildings around. You can’t drive there any more because no vehicle is allowed to pass there. A European-style fountain(喷泉) has been built in the street center garden.There used to be an old school near my house. I spent my five years studying there. There was a small payground in front of the school. But now what I can see are five tall buildings standing there. There are two big classroom buildings and a library. A new post office has also been built just across from the new school.【小题1】I have been away from my hometown for ________.A．ten months B．one year C．five years D．ten years 【小题2】On the right of my house, there was a _________ ten years ago.A．library B．garden C．supermarket D．pool 【小题3】No vehicle is allowed to pass the _________.A．center of the city B．old school C．street center D．playground 【小题4】Which of the following is WRONG(错的)?A．A fountain is in the street center garden. B．Now there is an old school near my house. C．There are two big classroom buildings and a library in the new school. D．There is a post office across from the school. 【小题5】What’s the best title for the passage?A．Great Changes in My Hometown. B．A Wonderful Place C．What a Nice Town D．My School.