阅读理解。

   Your brain controls everything you do. It makes it possible for you to think,

Learn, create and feel; to blink(眨眼) and breathe and for your heart to heat –this fantastic control center is your brain. It is so amazing that a famous scientist once called it "the most complex(复杂) thing we have yet discovered in our universe".

Can this small grey organ(器官) , which weighs less than one and a half kilos, really do so much? Amazingly , your brain contains about 100 billion neurons(神经元) -it would take you over 3, 000 years to count them all. Believe it or not, the activity in your brain never stops. Your neurons create and send more messages than all the phones in the world. And although one neuron creates only a little electricity, all your neurons together can produce enough electricity to power a light bulb (灯泡).

    So exactly how fast does your brain work? Well, imagine this: a bee lands on your foot. Neurons in your skin send this information to your brain at a speed of more than 240 kilometers per hour. Your brain then uses other neurons to send the message back to your foot to shake the bee off quickly. These neurons can send this information at more than 320 kilometers per hour. No computer has your brain's unbelievable ability to deal with the amount of information coming from your eyes, ears and other sensory organs.

    But how does your brain allow you to learn things that you will use in the future? The structure (结构) of your brain changes every time you have a new thought, remember or learn something. For example, riding a bike seems impossible at first, but soon you are able to do it. How? As you practice, your brain sends "bike riding" messages again and again soon, the actions are learnt and you are able to ride a bike easily from then on.

    Twenty years ago in Costa Rica, three girls found a baby sloth（树懒）on a road. The little animal's mother was killed by a car. These girls took the baby sloth to Judy, the owner of a hotel. Judy wanted to help, but she didn't know how to look after the sloth, so she called the zoo. With the help of the zoo, Judy took good care of the baby sloth. She named the baby sloth Buttercup.

    After her success, more people brought Judy wounded sloths or baby sloths they found. Judy then opened a rescue centre（救助中心）. Today, the rescue centre has saved more than 500 sloths. Sloths live in the forests of Central America and South America. They hang on to the trees with  their claws（爪子）. There are two main types of sloths. You can tell them apart by the number of their claws. Sloths hardly move. They spend most of their time sleeping in the trees.

    But now, with the increase of population, human beings（人类）cause a lot of problems for these slow and quiet animals. The main problems is that the forests are becoming smaller and smaller. When trees are cut down, sloths will fall and break themselves. Sloths who live near human beings sometimes are hit by cars or attacked by dogs.

    At the centre, workers care for the injured animals. Their goal is to help the sloths return to the wild when are healthy enough.

    Have you ever stayed in a hotel? Most Chinese hotels often provide guests with things like disposable (一次性的) toothbrushes, toothpaste, shampoo and slippers. Many guests like the idea because they don't have to bring their own. But, if you travel to Beijing, remember to bring your own things. Starting from June, some hotels in Beijing will no longer provide guests with these disposables. They want to ask people to use less disposable things.

    Many disposable things are made of plastic. People throw them away after only using them once. It is a waste of natural resources (资源) and is very bad for the environment. Do you know, one Chinese person makes as much as 400kg of waste a year! Most of that waste comes from disposable things. In Beijing, people throw away about 19,000 tons of plastic bags and 1,320 tons of plastic lunch bowls every year! Plastic can take between 100 and 400 years to break down. So the less plastic we throw out, the better. So, wherever you travel, bring your own things and use them again and again.

    Back at home and school, you can also do something to make our world a better place. Try to do these things in your daily life: Use cloth shopping bags, not plastic ones. After using a plastic bag, wash it out and let it dry. Then you can use it over and over again. Do not use paper cups. At your school canteen(食堂), use your own bowl and chopsticks instead of disposable ones.

    The air pollution was so bad in Harbin, in China, on October 21, 2013 that the city had to close roads and schools, and cancel hundreds of flights from its airport.

    News reports said the smog (a mixture of smoke and fog) was so thick that people couldn't see more than 10 or 20 metres in front of them.

    It is also said that people could not even see the person standing next to them. The city's website said: "You can't see your own fingers in front of you."

    The local people said there was a "burning" smell in the air. Many people covered their noses and mouths with scarves or masks.

    The pollution was caused on several factors including: farmers burning off old corn stalks and crop stubble; coal-fired heating systems; and low winds that allowed the smoke to remain over the city.

    The smog had been building up for several days. It became worse when the city turned on the public heating system, which uses coal to heat millions of homes and offices in the city.

    Harbin has a population of more than 10 million people. It lies in northeastern China, where cold winter weather can last up to six months. The main fuel there is coal, because it is cheaper than other types of fuel.

    Air pollution from burning coal can cause health problems like heart disease. During the smog crisis* in Harbin, the number of people taken to the hospital with breathing problems was 30% higher than usual.

    The city government is trying to reduce its use of coal by adding more insulation and better roofs and windows to buildings to reduce heating needs. It has also used cleaner fuel for cars and factories.

    When someone says, "Well, I guess I'll have to face the music", it doesn't mean that he is planning to go to hear a singer or attend a concert. It is something far sadder than you are called in by your leader to explain why you did this and that or why you did not do this or that.

    At some time or another, every one of us has to "face the music", especially as children. We can all remember Father's angry words "I want to talk to you". And only because we did not listen to him. What a bad thing it was!

    In the middle or at the end of every term, we students have to "face the music". The result of the exam will decide whether we will face the music or not. If.…that means parents' cold faces and contempt (轻蔑) of the teachers and classmates.

    The American novelist James Fennimore Cooper said in 1851 that the expression "face the music" was first used by actors while waiting aside to go on stage. When it was their turn to go on the stage, they often said, "It's time to face the music." An actor might be frightened or nervous as he moved onto the stage in front of the audience because they might be friendly, or perhaps they are hostile, especially if he forgot what he would say. But he had to go out. If he did not, there would be no play. He would lose his job.

    "To face the music" is well known to every American, young or old. It is at least 100 years old. It really means that you have to do something, no matter how terrible the whole thing might be, because you know you have no choice.