Think about vitamin D when you're catching up on summer rays. It's sometimes called the “sunshine vitamin” because it's produced in your skin in response to sunlight. Vitamin D is a fat-soluble (脂溶性的) vitamin in a family of compounds that includes vitamins D-1, D-2, and D-3. It can affect as many as 2,000 genes in the body.

    Vitamin D has several important functions. Perhaps the most vital are regulating the absorption of calcium and phosphorous（磷）, and promoting normal immune system function. Getting enough vitamin D is important for normal growth and development of bones and teeth, as well as improving resistance against certain diseases.

    In addition to its primary benefits, research suggests that vitamin D may also play a role in: reducing your risk of multiple sclerosis（多发性硬化）, according to a 2006 study published in the Journal of the American Medical Association decreasing your chance of developing heart disease, according to 2008 findings published in Circulation helping to reduce your possibility of developing the flu, according to 2010 research published in the American Journal of Clinical Nutrition regulating mood and warding off depression losing weight or preventing heart disease.

    How do you get it? Your body produces vitamin D naturally when it is directly exposed to sunlight. A little can go a long way. All you need is 10 minutes a day of midday, pre-sunscreen sun exposure,especially if you have fair skin. Besides getting vitamin D through sunlight, you can also get it through certain foods and supplements to ensure adequate levels of the vitamin in your blood.

    Do you know how it is when you see someone yawn and you start yawning too? Or how hard it is to be among people laughing and not laugh yourself? Well, apparently it's because we have mirror neurons (神经元）in our brains.

    Put simply, the existence of mirror neurons suggests that every time we see someone else do something, our brains imitate (模仿)it，whether or not we actually perform the same action. This explains a great deal about how we learn to smile, talk, walk, dance or play sports. But the idea goes further： mirror neurons not only appear to explain physical actions _y they also tell us that there is a biological basis for the way we understand other people.

    Mirror neurons can undoubtedly be found all over our brains, but especially in the areas which relate to our ability to use languages, and to understand how other people feel. Researchers have found that mirror neurons relate strongly to language. A group of researchers discovered that if they gave people sentences to listen to ( for example ："The hand took hold of the ball" ) , the same mirror neurons were triggered as when the action was actually performed (in this example, actually taking hold of a ball).

    Any problems with mirror neurons may well result in problems with behavior. Much researeh suggests that people with social and behavioral problems have mirror neurons which are not fully functioning. However, it is not yet known exactly how these discoveries might help find treatments for social disorders.

    Research into mirror neurons seems to provide us with ever more information concerning how humans behave and interact(互动）.Indeed, it may turn out to be the equivalent (相等物）for ncurosciencc of what Einstein's theory of relativity was for physics. And the next time you feel the urge to cough in the cinema when someone else does--well，perhaps you'll understand why.

    There have always been a lot of commonly believed but false ideas about being fat and doing exercise. Some people believe that they can't help putting on weight as they get older, while others hold that if they stop exercising, their muscles will turn into fat. Here are some more myths：

    I'll never lose weight—I come from a fat family

    Wrong! While we can't change the body type we are born with, we can't blame our genes for making us fat. There's plenty of evidence that fatness runs in families, and the main reason is that they share the same habits of eating too much and exercising too little.

    I am fat because I burn calories slowly

    Wrong! Fatness is not caused by a slow metabolism(新陈代谢). In fact, although fat people consume more energy than slim people, they also fail to realize how much they eat! Keeping a diary can help you work out your daily food intake more accurately.

    Exercise is boring

    Wrong! Anything will become boring if you do it repetitively. The key is to develop a balanced and varied programme that's fun as well as progressive. If you enjoy a Sunday walk, take a different route. If you do yoga, try a tai chi class. If you like swimming, set yourself a distance or time challenge.

    No pain, no gain

    Wrong! Exercise is not meant to hurt. Indeed, pain is your body telling you something's wrong, and continuing to exercise could lead to serious injury. You may experience mild discomfort as you begin to exercise regularly, but this is your body adapting to the positive changes in your lifestyle and the aches should disappear relatively quickly. If they don't, rest and seek medical advice.

    It's nice being nice to others; it's also great to give people a hand. However, if you start to hurt yourself by doing so, then this is not so healthy.{#blank#}1{#/blank#}If you fear that you might fall into this category, the following tips will help you to stand up for yourself and regain your self-confidence.

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    Although you may often stay silent if something is wrong or bothers you, it is better to speak your mind right away. You don't have to be rude, but you do have to be firm and direct. Don't do things for others if you don't really want to. Speak up, and soon others will be seeing you in a whole new light.

    Start small.

    {#blank#}3{#/blank#}This will allow you to practice being brave and self-confident. Tell a person who has cut in line in front of you to move to the back of the line, or tell a salesperson to do that. Before long, you will be confident enough to stand up to your friends and family members.

    Judge well.

    When dealing with others, you have to exercise good judgment. {#blank#}4{#/blank#}If a colleague isn't doing his part, you should rightfully demand that he start doing so. However, if a taxi cuts you off in traffic, just let it go.

    {#blank#}5{#/blank#}Rome wasn't built in a day. If you want to get back again after having been a pushover(耳软心活的人), it's best to take one step at a time.

A. Express yourself.

B. Regain your confidence.

C. Start by speaking up for yourself with strangers.

D. Everyone has the right to live without being judged.

E. If you slip back into the pushover mode every once in a while, don't blame yourself.

F. Sadly, some people are so easily pushed around that they come to be seen as pushovers.

G. It's one thing to be confident, but quite another to forcefully say no to an unreasonable request.

    Putting a dinosaur skeleton(骨架)together is not easy. The skeletons are usually very incomplete. Many dinosaur fossils(化石) are discovered badly damaged. Bones are often found crashed (压碎) or bent by the great weight of the dirt and rock above. Sometimes parts from different creatures are mixed together. This just adds to the confusion.

    Unfortunately, some scientists have not been careful enough in their descriptions of dinosaurs. They have told grand stories of how dinosaurs looked and behaved. All of these descriptions are based on guesswork – the imaginations of people who have never seen a living dinosaur. Some scientists have made complete pictures of dinosaurs based on just a single bone or tooth or leg. Such pictures are based on many guesses and very little facts. The scientists' ideas often turn out to be wrong when more facts are discovered.

    Dinosaur fossils are not found with labels attached showing what the animals looked like. That is why no pictures of dinosaurs are exactly right. Every dinosaur painting is sure to contain at least some wrong information. No artist in the twentieth century ever saw the living, breathing animals -- complete with skin, flesh, and color.

    For instance, imagine never having seen or heard of a peacock. One day you find the jumbled bones of it buffed in the ground. You try to put the bones together to form a skeleton. And then you try to draw a picture of what the animal looked like when it Was alive. But bones cannot tell the whole story. Even if you are a very good artist, it would be a miracle if you drew a tree picture of a peacock just from the bones and your imagination.

Humans' voice sounds more pleasant than that of primates（灵长类动物）because we don't have vocal membranes （声带膜）, a new study suggests.

Humans have vocal cords（声带）, muscles in the top of the throat, which vibrate（振动）to produce sound. That unique part helps people control their voices well enough to produce sounds that form spoken language. However, unlike all the other studied primates, humans don't have vocal membranes.

To find out how vocal membranes affected spoken sounds, a team from Kyoto University took throats from monkeys that had died of natural causes and put the parts into devices, pushing air through the throats to see how the vocal cords and membranes would react. In the experiment, the researchers found that their vocal membranes and vocal cords vibrated together.

Researchers said these vocal membranes make it harder for other primates to control the voices they make. Without these membranes, humans vocal source is more balanced, allowing better voice control and production of long and balanced voices. A key thing that distinguishes human speech from animal sounds is our control over the sounds we make.

In humans, that sort of unpleasant voices can happen when we put extreme amounts of pressure on our voice, like baby crying and adult screaming. But those are rare cases. Researchers also said that our mouths and tongues could help control the voices. They are the basis of human languages.