Many animals use some kind of “language”. They use signals(信号)and the signals have meanings. For example, when a bee(蜜蜂) has found some food, it goes 1 home. It is 2 for a bee to tell 3 bees where the food is by speaking to 4, but it can do a little dancing. This tells the bees where the food is and 5 it is.
Some animals show how they feel by making sounds. It is not difficult to 6. If a dog is angry, it barks(吠). Birds make several different sounds and 7 has its own meaning. Sometimes we humans make sounds 8. We make sounds like “Oh!” or “Ouch!” to show how we feel about something or when we 9 something on our feet.
We humans have languages. We have words. These words have the meaning of things, actions(行动), feelings or ideas. We 10 give each other information. Writing down words, we can remember what has happened or send messages to people far away.
根据短文内容，选择最佳答案。
Plants are very important. This is because plants can make food from air, water and sunlight. Animals and man cannot make food from air, water and sunlight. Animals can get their food by eating plants and other animals. Man gets his food by eating plants and animals, too. So animals and man need plants in order to live. This is why there are so many plants around us.
There are two kinds of plants: flowering plants and non-flowering plants. Almost all the trees around us are flowering plants. You can know some trees from their flowers and fruit. Non-flowering plants do not grow flowers. You cannot see many non-flowering plants around you.
If you look carefully at the plants around you, you will find that there are many kinds of plants. Some plants are large and some are small. Most of them are green. Thanks to the plants around us we can live on earth.
Now many people like to keep dogs as their pets. But how did dogs become humans' close friends?
In some places of Europe (欧洲), about 10,000 years ago, some wild (野生的) dogs often came to human's houses to find food. The wild dogs looked different from the ones today. They looked like wolves (狼). At first, they felt ① frightened. They always stood and looked for a short time. Then they got the food and ran away. Sometimes the young dogs couldn't run fast and people caught them. People trained them and the young dogs grew up with the help of people. Slowly, the wild dogs became home dogs. They could make home safe when people were away. They helped people hunt (狩猎). They helped people keep warm on cold nights. ② Sometimes, they could smell and hear danger before people could. In some cold places, they helped people pull (拉) things people need.
Now there are more than 400 different kinds of dogs in the world. And they look different from each other. The number and kind are growing all the time. Today, some people mainly (主要地) regard dogs as pets. In fact, dogs are really our close friends. We should protect them from being killed.
What could dogs do for humans long long ago?(不少于2条)
