阅读短文，根据短文内容回答问题。
We've all heard of mermaids. They are the beautiful half-human, half-fish creatures(生物). They have the head and body of a human and the tail of a fish. We also know that mermaids only exist in fairy tales. But where did all the stories about these creatures come from? If you have ever seen a manatee, then you might have an idea.
Manatees, which are also called sea cows, are mammals(哺乳动物) that live in the sea. Since they are mammals, they have to swim up to the surface to breathe air. Many people believe that the story of the mermaid began with the ancient sailors who saw the manatees putting their heads out of the water to breathe. Because manatees are upright when they do this, it looks like they are standing. If a sailor saw a manatee doing this from far away across the sea, it is possible that the sailor would mistake the manatee for a creature that is half-human, half-fish.
Mermaids are described as having very long hair. This is probably because manatees like to swim up to the surface of the water in areas where there is sea grass. Manatees eat all kinds of plants in the sea, including sea grass. The sea grass around the manatee's head when they eat could create a picture of long hair.

Manatees also have powerful tails that are very similar to the fish-like tail of a mermaid. The sailors probably watched manatees come up for air and then swim back below the surface, using their paddle-shaped tails. This would explain why the sailors thought mermaids had fish-like tails.

    This is a home of the future, a "smart home", where technology can do almost everything. Imagine we are in the year 2050, ①the computer wakes Tom up in themorning as usual. In front of him is a to-do list of the important events for the day, and it is provided by the computer too. According to Tom's request, the computer serves a list of possible dishes. All the dishes are nice.

    As Tom eats breakfast, the computer reminds him to reply to Lucy. Before Tom finishes his next bite, Lucy's computer receives the message. Then Tom goes to the supermarket. The store's system checks his car when he drives to the pickup area and greets him by name. "Good morning, Tom! Your order is in Case4. Thank you for shopping.'' When Tom removes his order from Case 4, all trades are completed automatically(自动地)over the information superhighway. That is, the money is electronically paid into the bank. Soon after arriving at the office, Tom reads another message from Lucy, telling him that she will go to dinner with him.

    The smart home can also do many other things:

    ◆Find things like keys and mobile phones.

    ◆②        (打开或关闭)machines and lights with your voice.

    ◆Clean your home from clothes to buildings automatically.

    ◆Record everything and everyone entering and leaving the house.

    ◆Take care of each member of the family, young or old.

    ③With the development of technology, the smart home will come true in the future. It is sure to play an important part in our life.

    Robots are playing an important role in our life. They can help people a lot.

In our homes, robots are useful. They can help us do some cooking. They can help the blind (盲人) read newspapers and help the old people move some heavy things. They can play chess with children.{#blank#}1{#/blank#} They are people's best friends.

    {#blank#}2{#/blank#} They work faster and do not need a rest. People will get bored if they do the same work over and over again{#blank#}3{#/blank#} And they can do some work in the dangerous or dirty places{#blank#}4{#/blank#} 

    However, robots are not as clever as people.{#blank#}5{#/blank#} If we do not “teach” them how to do things first, they can do nothing.

根据短文内容，从方框中选出五个句子填入文中空缺处，使短文内容完整正确。

A. They can't think like us.

B. Usually people can't.

C. But the robots will not.

D. In factories, robots can help people do a lot of work, too.

E. They can also help children learn English and other subjects.

F. They can think like people.

We've talked about snails (蜗牛) and their slow move . But much of the time snails don't move at all. They're in their shells (壳)—sleeping .

    Hot sun will dry out a snail's body. So at the least sign of hot sun, a snail draws its body into its shell and closes the opening with a thin cover .Then it goes to sleep. A snail will die in a heavy rain. So whenever it rains, it goes inside its shell house and goes to sleep. A snail can sleep for as long as it needs to. It can take a short sleep. Or it can sleep for days at a time .And it spends all the winter months in its shell, asleep.

    In spring the snail wakes up .Its body, about three inches long, comes out of from the shell. When hungry, the snail looks for food. It can't see very well. Its eyes ,at the ends of the top feelers (触角)are very weak . But its sense of smell is very strong. It helps the snail to the new greens. Then the snail's little mouth goes to work.

    A snail's mouth is no longer than the point of a pin(针) . Yet it has 256,000 teeth! The teeth are so small that you can't see them. But they do their work. If you put a snail in a hard paper box, it will eat its way out. And if a snail wears out its teeth, it will grow new ones.

    Mostly, a snail looks for food at night .But on cloudy days it eats in the daytime. It eats all day long. A snail can go on eating for hours and never feel full.

    Albert Einstein is right once again! He thought of the idea about gravitational waves years ago with his Theory of Relativity, but scientists are finally discovering that it really exists now. But what are gravitational waves, and why are they important?

    Well, gravitational waves are made by black holes and can change time in space. Black holes aren't holes but are lots of matter put together into a very small area. They are created when a star, much like our sun, explodes and leaves behind this dense* material. It doesn't shine like a star any more, and it becomes black.

    The black holes that made these waves are special. About 1.3 billion years ago, there were two black holes that kept moving closer and closer together. Finally, they hit each other and formed one big black hole. The energy is given off and created the ripples* in space. These ripples are gravitational waves. For example, imagine you throw a stone into a pool. It creates ripples that change the shape of the water. Well, that's kind of what the influence of one black hole hitting the other has in space.

    Gravitational waves are hard to explore. But thanks to the efforts of scientists, the ripples were discovered on Feb. 11th, which is the first time in human history. Einstein was excellent to know this 100 years ago before we have the technology. It can give us a new view of the universe we live in. The discovery of gravitational waves, unlike stars, galaxies and other bright objects, black holes don't produce light, so we can't see them by tools. Gravitational waves allow scientists to look at the universe not only with light, but also with gravity. "Everything else in astronomy like the eye," A scientist told The New York Times. "Finally, astronomy grew ears. We had never ears before."

    Now, we will be able to find black holes and things that are much further away from Earth, which means much more space exploration in the future. And who knows, this discovery could even lead to time travel!

    In 1845, a deadly disease struck the farms of Ireland, killing all the Lumper potato plants. In another place or time, the death of single crop species (物种) might not have been so important. But in Ireland, in 1845, people depended almost solely on the potato for food. The death of one species caused a terrible famine(饥荒). Now, some scientists are worried that such a famine could happen again, but on a much wider scale.

    Over the centuries, farmers have discovered thousands of different species of food crops. Each species has special qualities. Some can be grown in very hot or cold climates. Others are not affected by certain diseases. However, you won't find many of these species in your local supermarket. To feed the seven billion people on Earth, most farmers today are growing only species of plants and farming only species of animals that are easy to produce in large numbers.

    For example, in the Philippines, there were once thousands of varieties of rice: now fewer than 100 are grown there. In China, 90 percent of the wheat varieties grown just a century ago have disappeared. Scientists believe that over the past century, we have allowed more than half of the world's food varieties to disappear.

    One solution to this problem is to collect and store the seeds (种子) as many different plant varieties as we can before they disappear. The idea was first suggested by Russian scientist Nikolay Vavilov. In the 1920s and 1930s, he collected around 400,000 seeds from five contients. More recently, others are continuing the work he began.

    In the U.S. state of Iowa, Diane Ott Whealy wanted to protect historic plant varieties, like the seeds her great –grandfather brought to the U.S. from Germany more than a hundred years ago. She and her husband started a place called Heritage Farm, where people can store and trade seeds.

    More importantly, the people at Heritage Farm don't just store the seeds; they plant them. By doing this, they are reintroducing foods into the marketplace that haven't been grown for years. These food species are not just special in terms of appearance or taste. They also offer farmers food solutions for the future, from the past.