Let's try doing the following experiment.

 What to do：

 Use string to hang a paper clip or other small object at about chest（胸部）level.

 Pick up a stick，such as a broom handle. Take three or four steps away from the paper clip.

Now close one eye and walk toward the paper clip. Try to touch it with the tip of the stick. If you miss，try again，still keeping one eye closed. Now try it with both eyes open and see if it's easier to do.

 How it works：

 In the experiment，you have to judge how far away the paper clip is. Your brain has several ways of doing this.

 One simple way depends on how much your eye has to focus（聚焦）itself. Using only one eye，most people will find it difficult to touch the paper clip on the first try，but the brain still gets some information about distance—though not much.

 Your brain can judge distance much better when you look at something with both eyes. In fact，your brain has more than one way to use both eyes in judging distance. For example，to see anything clearly，you have to make both of your eyes point at the object. When you look at a nearby object，your eyes turn inward. You can feel this happening if you look at the tip of your finger and move your finger toward your nose.

 Your brain gets information from the eyes about how much they are pointing toward each other. Using that information，the brain can tell how far away any object is，whether it is a basketball or a paper clip.

阅读理解

    American Sign Language, often called ASL, is used by most people with hearing problems in the United States and Canada.

    Besides ASL, there are more than fifty sign languages used throughout the world today, including Mayan Sign, British Sign, Israeli Sign, and Chinese Sign. Like spoken languages, sign languages are different from each other. But all sign languages are based on sight instead of sounds.

    Sign languages have several main visual (视觉) parts that work together to express meaning. The first part is the shape made by the hands. Movement is also important. Moving the body or organs (器官) like hands affects the meaning of the shape. The place where the sign is made and the direction the hands face are crucial as well. Other visual clues (线索), such as the expression on a person's face, can sometimes change a sign's meaning. For example, a change in a smile can show whether a signer is happy, very happy, or overjoyed. Raising the eyebrows can mark a question.

    In sign languages, the visual parts are combined (结合) in different ways to create signs.

These signs stand for things, actions, feelings, and ideas. ASL has about 4,000 different signs. Like spoken  languages,  sign  languages  cannot  be  translated  word-for-word.  

    For English word may be represented by a series of signs in ASL. Or several English words may be

represented by a single ASL sign. Unlike spoken languages, the signs are organized according to sign-language grammar and the most important word or idea is signed first.

    In ASL, the letter signs are made with one hand. Signers would rarely, if ever, spell out all the words they are signing. That would be as awkward and slow as speakers spelling each spoken word. However, American Sign Language does not have signs for proper names, so signers may use the alphabet to spell these. Also, sign languages often borrow words from other languages. They may spell words using finger spelling which is done with a set of hand shapes that stand for letters of the alphabet.

    Sign languages  develop  naturally  when  people  with  shared  culture  and  needs  want  to communicate with each other. Signers are closely linked to each other, perhaps more than to speaking people in their own communities. Signers share points of view, values, needs, and problems,as well as languages.

    Wouldn't it be funny if your mum said to you, "It's time for bed, honey. It's almost November!" Well, if you were a baby bear, your mother might let you know it's time to go into a deep sleep around October.

    That "deep sleep" is called "hibernation (冬眠)". When it gets cold, bears have to go into hibernation. By taking this long sleep, they can get through the cold months when the food, like berries (浆果) and nuts, cannot be found easily.

    Have you ever heard someone say that they are as hungry as a bear? Bears need to eat a lot of food before hibernating. They eat so much that they may put on forty pounds of fat in a week. During the winter "bears will live off the fat stored in their bodies. Bears are able to do that because their bodies use a lot less energy during hibernation. Their heartbeats slow down, their breathing slows down, and their body temperature drops.

    If you were going to sleep all winter, wouldn't you want to be in a safe and protected place? That is what a bear wants, so it looks for a cave to sleep in. It makes a bed using grass, leaves and twigs (嫩枝). The bear usually starts to hibernate as early as October and doesn't wake up until April or May. By the time the bear wakes up, it will have lost much of the fat. But spring time will bring much food to enjoy until it is time to hibernate again in the autumn.

    Brooke wanted a dollhouse and some sugar cookies. So the 6-year-old asked Alexa to get them. Alexa wasn't her mom or babysitter. It was a voice-activated home assistant powered by AI (人工智能). And it made Brooke's wishes come true. A few days later, much to her parents' surprise, a $170 dollhouse and four pounds of cookies showed up. They ate the cookies and gave away the dollhouse to a local hospital. And that's not the end of the story. When a news reporter told the story of what happened on TV, Alexa devices (设备) in many listeners' homes woke up and tried to order dollhouses!

    Alexa isn't the only AI willing to serve you. Apple Home Pod has Siri, Google Home has its Assistant, and the upcoming Galaxy Home device will have Bixby. People who have these devices use them mainly for listening to music, checking the weather, and setting timers. According to a report from The Information, nowadays voice shopping is rare. But many scientists predict a boom (增长) in voice shopping in the near future. Is that a good thing?

      ▲   You can shout out an order as soon as you think of it, even if you are cooking, cleaning, or driving. In addition, people with disabilities who are unable to use a keyboard or mouse can shop without any help.

    But voice shopping has its disadvantages. Unwanted dollhouses aren't the biggest problem. It's usually very easy to cancel an order or return products. The thing that worries some people is that these assistants are always listening. They have to be able to respond when you want them. So they listen for "Alexa" or "OK Google" or another order. When they hear it, they start recording the conversation. Some have worried about what happens shopping habits? And what if someone hacks (入侵) the device? The CIA found a way to hack smart TVs to turn them into spies that listen all the time. Others could do the same with any smart device.

    What do you think? Are you ready to start voice shopping?

    When I was a little girl, my family lived in the countryside. There was a beautiful river near my home. The water was clean and cool. I liked to go fishing there with my mother. We would catch fish, look for clams(蛤)and play in the water. There were also a lot of birds near the river. We would spend all day watching the birds.

    Now my family live in the city. Last Sunday, my daughter asked me to take her to see the river I was always talking about. "I want to go fishing there so much with you and Grandma," she said.

    When we went to the river, we only saw a factory and a mountain of waste. My mother was surprised, my daughter was disappointed, and I was sad. The river was my best friend. I grew up with it. Now there are no fish in it, and the birds have gone too. I hear them crying for help. But what can I do?