[解析]
18.B
19.B
20.C
【原文】
Boys and girls,please stay together.Let's hurry up and begin our class trip to the museum.The visit starts on the first floor.Pay attention to the information about the technology in the old days.Spend as much time as you can looking at everything,because we won't come back.
Then we'll go upstairs to the second floor.After we arrive at the Inventors of the 20th Century Room,please read the invention stories and look at some modern inventions as well.While you look at these inventions,think about how they can make our lives more comfortable.
When you have finished looking at the things on show,take a lift up to the third floor.You can go to the cafe for a drink,but don't stay too long.
If you want to know more about the museum,you can buy books or magazines,or ask the guide for help.Remember,the most helpful way is to search the museum's website.I'm looking forward to reading the reports about your visit next Monday.