When we can see well, we do not think about our eyes very often. It is only when we cannot see perfectly that we come to see how important our eyes are.

    People who are nearsighted can only see things that are very close to their eyes. Many people who do a lot of close work, such as writing, reading and sewing（缝纫）, become nearsighted. Then they have to wear glasses in order to see distant things clearly.

    People who are farsighted（远视的）suffer from just the opposite problem. They can see things that are far away, but they have difficulty reading a book unless they hold it at arm's length. If they want to do much reading, they must get glasses too.

    Other people do not see clearly because their eyes are not exactly the right shape. This, too, can be corrected by glasses. Some people's eyes become cloudy because of cataracts（白内障）. Long ago these people often became blind. Now, however, it is possible to operate on the cataracts and remove them.

    When night falls, colors become fainter to the eye and finally disappear. After your eyes have grown used to the dark, you can see better if you use the sides of your eyes rather than the centers. Sometimes, after dark, you see a small thing to one side of you, which seems to disappear if you turn you head in its direction. This is because when you turn your head, you are looking at the thing too directly. Men on guard duty sometimes think they see something moving to one side of them. When they turn to look straight at it, they cannot see it any more, and they believe they were mistaken. However, this mistake happens because the center of the eye, which is very sensitive(敏感的) in daylight, is not as sensitive as the sides of the eyes after dark.

    Camels are large animals living in dry areas. There are two species of camels; the Arabian camel with a single hump(驼背) from the dry desert areas of West Asia, and the Bactrian camel with two humps from Central and East Asia. Camels are over 7 feet tall and weigh over 1,600 pounds. They will live up to 40 to 50 years. Most camels are domesticated(驯化) and fed by people. Camels are plant-eaters．

    Camels are very strong animals with wide, padded feet. They have thick leathery pads on their knees and chest. Camels have nostrils(鼻孔)that can open and close, protecting them from the desert environment. Bushy eyebrows and two rows of long eyelashes protect their eyes from sand. Their mouth is extremely tough, allowing camels to eat thorny(带刺的)desert plants. Their widened feet help them move without sinking into the sand. Their thick coats reflect sunlight, and also protect them from the intense heat from desert sand. Their long legs help by keeping them further from the hot ground．

    Camels can go without food and water for 3 to 4 days. They do not store water in their humps as is commonly believed．The humps are actually a container of fat. Camels are incredibly well-adapted to their environment. When conditions heat up, camels can increase their own body temperature, which prevents sweating and therefore water loss. They may not sweat at all during the day．

    Camels are sometimes called“ships of the desert”because people ride them around the hot, dry deserts of the world．However, the number of camels is becoming smaller for various reasons．

It's a popular belief that a fish's memory lasts for only seven seconds. It may seem sad to think that they don't remember what they've eaten or where they've been, and they don't recognize you or any of their friends—every moment in their life would be like seeing the world for the first time.

    But don't be so quick to feel sorry for them. A new study has found that fish have a much better memory than we used to think. In fact, certain species of fish can even remember events from as long as 12 days ago.

    In the study, researchers from MacEwan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They then waited for 12 days before putting them back in the tank again.

Researchers used computer software to monitor the fish's movements. They found that after such a long break the fish still went to the same place where they first got food. This suggested that they could remember their past experiences.

    In fact, scientists had been thinking for a long time that African cichlids might have a good memory. An earlier study showed that they behaved aggressively in front of certain fish, perhaps because they remembered their past “fights”. But until the latest findings, there was no clear evidence.

    Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild.

    “If fish are able to remember that a certain area contains safe food, they will be able to go back to that area without putting their lives at risks,” lead researcher Trevor Hamilton told Live Science.

    For a long time, fish were placed far below chimpanzees, dolphins and mice on the list of smart animals. But this study has given scientists a new understanding of their intelligence.

    Inside the Rain Room

    The Rain Room has arrived and local art lovers are taking notice. Is it worth the wait? Yes, I assure you it is. Once inside, visitors find a long, dark room with a high ceiling. A single bright light shines through heavy rain falling around visitors. The mist. The damp air. The noise. It feels like a mighty storm is pouring down. But the storm is inside. And visitors aren't getting wet. Instead, visitors wander in awe, admiring the rain and the artists who created it.

    The Rain Room was created to highlight the connection between humans, nature and technology. With a tracking system that senses movement and stops the rain wherever visitors move, it does just that. Light and sound produce an experience that feels both natural and foreign. The exhibit is moving on to Atlanta next month. I urge you to visit before then. It's time to experience the Rain Room for yourself!

    Welcome to the Rain Room

    The Rain Room features falling water. Please be aware you may get slightly wet. However, visitors wearing raincoat will be turned away.

    This exhibit features advanced technology. To ensure its effectiveness, please avoid wearing dark or reflective clothing.

    Visitors are welcome to take photographs of the exhibit.

    Children must be accompanied by an adult.

    For the convenience of all guests, visits are limited to 10minutes.

    Chris Mazdzer won a silver medal in a men's luge (无舵雪橇) singles event at 2018 Pyeongchang Winter Olympics, South Korea — equaling the best finish ever for any member of the US Olympic luge team. In the luge, competitors lie flat, feet first, on a small sled (雪橇). They can travel around an icy track at speeds up to 140 kilometers an hour. The riders control the sled's speed by changing the position of their feet or by moving their shoulders.

    So why did the US luge team win a medal at the Pyeongchang Olympics? Most credit must go to Chris Mazdzer himself. The American said his win was a product of 16 years of preparation and intense training. But another reason for Mazdzer's success could have been the 3-D printing technology, which his team used to make its equipment.

    The term 3-D is short for three dimensional, meaning an object with length, width and height. In 3-D printing, 3-D models are first created as files, or documents, on a computer. The printer then uses a substance (物质) like plastic or metal to create physical objects. The process involves making one layer of material at a time until the objects reach full form.

    The US luge team worked with an American company called Stratasys on the designing and manufacturing process for the sleds. First, the company made a scan, or image, of the body of every member of the luge team. Then, 3-D printing technology was used to create tools for making molds (模子) in the shape of Olympians on top of a sled. The process of designing and tooling sled parts is highly complex and can take several weeks. Officials from the US luge team say 3-D printing can greatly simplify the process, speeding up the production of parts.

    Jon Owen, says the use of 3-D printing has made the team more competitive. It helps the team “continuously adjust designs and run the sleds on the track much faster than traditional processes,” he said. He added that the technology also provides a way to perfectly fit each rider to the sled, while cutting production time and costs.

Throughout our lives,we have been told to take care of our physical health.But what is often ignored is mental health.That's why World Mental Health Day was created.{#blank#}1{#/blank#}.

When is World Mental Health Day?

World Mental Health Day is on October 10th.Though there is one specific date for it,it is often times celebrated and observed over the course of a week.{#blank#}2{#/blank#}, it allows more people to know about the importance of mental health and it educates the public about the "why", "how" and "what" of mental health.

What is the history of World Mental Health Day?

{#blank#}3{#/blank#}.When it first started,the day had no theme,but instead was an excuse for medical workers to educate the public on what was not always openly discussed — what mental health is and the issues that surround it.Mental health affects everything from our emotional state to our physical state,and everything in between.In the first few years,organizers usually hosted a global live broadcast,leading to live telephone participation from all over the world.

{#blank#}4{#/blank#}?

You can volunteer in or donate some money to mental health services to improve the livelihoods of people struggling with mental illnesses.Besides,too often we are too busy to slow down and take a breath.If you take a mental health day,you are giving yourself the space to grow and take care of your mental health.Lastly,you should check on your friends.Go for a walk with them or have an extended phone conversation if you are far away.{#blank#}5{#/blank#}.

A.Why mental health is so important

B.How to observe World Mental Health Day

C.By celebrating it in a week instead of a day

D.If we value the importance of mental health

E.The first World Mental Health Day began in 1992

F.In this article,let's explore World Mental Health Day

G.You might be surprised at how much you can help them relax