根据短文内容回答下列问题。

    It's March, 2050.

    Frank and Mary Smith wake up in their comfortable house in the morning and switch on the bedroom computer to get the latest news.

    They used to read the Times, but changed to electronic newspapers many years ago.

There is the usual news about space: another space flight has returned from Mars and scientists have discovered a new planet. Then they turn to business news: the US dollar has risen greatly in Shanghai, one of the world's leading business centers. Mary tells the computer to buy 5000 dollars, and there is a quick response that it has been done.

As they watch the screen, Mary orders one of the household robots to make coffee for them. Frank disappears into the study to join a video conference with his partners around the world. He is a computer engineer, working for several companies. This is his third job: he used to be in marketing and then television.

    Mary has a quick look at the shopping channels--the usual selection of electric cars, household robots and cheap travel offers before picking up the video phone to talk to her assistant. She also has a job and she is doing medical research. Both she and Frank used to have an office desk in London, but in 2014 they decided to move to the seaside and work from home.

    Frank and Mary have one daughter, Louise, who also has her own workstation at home. She goes to school only one day a week, mainly to play with other students. Classrooms disappeared in 2030 because there was no longer any need for them: communications systems have made it much easier to learn at home.

    Louise, now thirteen, is studying Chinese at present, which has become a world language as important as English. Louise has many Chinese friends. They communicate by computer.

    According to the family doctor, Louise will live to at least 130. Her wish is to work for a few decades(十年) and then spend her time on music and painting.

      Look up in the sky. Do you see any clouds? What do they look like ?Some clouds are fluffy（绒毛状的）and white, like cotton balls. Others are dark, almost black, and make you hold an umbrella. At sunrise and sunset, clouds can look red, purple, or yellow，as if they were colored with crayons. But what are clouds anyway?

   You can't reach out and touch the clouds, but you can make your own in a bottle.

   You need :

   An adult helper

   A huge, empty glass container（容器）

   A metal strainer（滤网）

   Hot water

   Ice

   Do these:

   Step1. Have your helper fill the container with hot water ,leave it there for two minutes, then pour out most of the water, leaving just an inch or two at the bottom of the container.

   Step2. It's your turn now. Put the strainer over the mouth of the container. Fill the strainer with ice. Watch the container.

What happened?

A cloud formed in the container! Some of the hot water at the bottom of the container turned into the hot water vapor. The water vapor rose and met with cold air coming off the ice. When the water vapor condensed（凝结）,it formed a cloud. Hot air rises ad carries with it lots of water vapor. The higher the air rises, the more it cools down. Soon the cold air can't hold all the water vapor so it starts turning into tiny water drops, and becomes a cloud.

    A city without cars would be very strange, right? But Venice is such a city.

    Venice is in the northeast of Italy. It wasn't built on land, like Beijing or Shanghai, but on more than 110 islands. Seawater is everywhere around the city.

    Even so, travel isn't difficult. The waterways have always been the best way to get around. There are 117 waterways and more than 400 bridges that can guide you where you want to go.  People in Venice move from place to place by boat.

    Water makes the city special, but it is also a big problem. Sometimes tourists will have such strange experiences. One moment they walk across the Rialto Bridge, and there's nothing special. But when they come back to the bridge an hour later, it's underwater and everyone is wearing rain shoes.

    Once, people used too much underground water. This made the city get lower little by little. Now the city has gone down by 23 centimeters. Another problem is the rising seawater. The temperature has risen over the years. This has made the ice of the Arctic Ocean (北冰洋) melt( 融化). Every year, high waters hit the city in autumn and winter. When a lot of water comes, more than half of the city is underwater.

    Scientists are trying different ways to stop the city from getting even lower. The Italian government has asked some of Italy's biggest companies to build the MOST project, which was planned to be build under the seawater to stop the rising water. Anyway, this project is helping solve the problem.

    In the universe, as we all know, there is the sun, the moon, the earth and a good many stars. Through our geography lessons, we know the earth goes around the sun, and the moon goes around the earth. We have day and night because the earth keeps turning all the time. When our part of the earth turns to the sun, it is day. When our part of the earth turns away from the sun, it is night.

Just because the moon is closer to the earth than the sun, it looks much bigger than the sun. Big things will look smaller when they are further, and small things also look bigger when they are nearer.

    The sun is big enough to give out very strong light. The moon can't give any light at all, but it looks quite bright, too. Why? In fact, the light from the moon comes from the sun. The moon looks much bigger and brighter than the stars. But actually (事实上) the stars are much bigger and brighter than the moon. They look smaller than the moon also because they are further away from the earth.

    There are many other planets in the universe. But of all the planets, only on the earth there are living things and people can only live on the earth, too. But at 9:00 a.m. on October 15th，2003, Chinese pilot Yang Liwei was sent up to space. He stayed there for 21 hours. It was the first time for Chinese to get into space.

    We all know that many inventions have changed our life a lot. They play important roles in our daily life. Here are some interesting inventions.