Early people lived by hunting animals and gathering grains. After a tribe(部落） had lived in an area for some time, its food supply would begin to reduce. Then the tribe had to move to new hunting grounds where there was more food.

    This way of life caused special problems for the tribes. They were forced to depend on luck, as well as on their hunting skills. If they could find no game, the whole tribe was in danger of starving. And when the hunters had good luck one day, they were not sure to find game the next time. The tribes moves often because much land was needed to support their people.

    Finally, people learned that they could grow their food. At first, the women of tribes raised patches of wild grain. Later, people discovered that they could plant their own seeds. Farming slowly became a way of life.

    As people turned away from hunting to farming, their life changed. When the food supply became more constant, they no longer moved from place to place. The success of their crops depended partly on the weather, but there were also things they could do to help crops grow.

    In the past, a tribe had to travel many miles for food. Now , only a small amount of land was necessary to feed the whole tribe. The tribe could grow in size because farming provided a way to feed people.

    Winter is a really fun time of the year—it's great to have snowball fights and build snowmen{#blank#}1{#/blank#} When it's cold outside and you're not prepared, you can feel uncomfortable. Lucky for you, learning how to stay safe is not difficult.

    ●{#blank#}2{#/blank#} Wearing thick clothes is the best way to stay warm in the cold. Depending on where you live and how cold it is, some kids may need more clothes, some less.

    ●Take that hat. You maybe wear a large overcoat and ready to go, but are you forgetting something?{#blank#}3{#/blank#} You'll stay much warmer with a hat than without one—tons of body heat escapes right from your head.

    ●Drink up. Sounds like advice for hot weather, not cold weather, right?{#blank#}4{#/blank#} When you're outside in the cold and breathing hard, your body loses a lot of water through your breath. And the best way to get that water back is to drink up!

    ●Take it easy. Sometimes if you're out having fun, it's easy to forget to pay attention to your body. But if your body temperature drops even 4 or 5 degrees while you're out side, it can make you feel terrible{#blank#}5{#/blank#} And if you ever feel weak, those are signs that you have to take it easy indoors for a while.

A.Love those clothes.

B.Have a snowball fight.

C. Pull a hat onto your head.

D. That's why you need to be careful with your body s signals.

E. Well, the truth is that it's good advice for both kinds of weather.

F. but you have to know how to be safe while you're out having fun.

G. You can stay outside as long as possible to fully enjoy your snow days.

    Everyone should be so lucky as to have a friend like Francia Raisa. On Thursday, singer and actress Selena Gomez, 25, used Instagram to explain why she was “laying low” this summer. She posted a photo of herself in a hospital bed with her friend Francia Raisa holding hands. She said she recently received a kidney transplant from her best friend because of complications（并发症）from lupus（狼疮）, an autoimmune disease, which means it is the result of the immune system attacking normal tissue, including the kidneys, brain, heart and lungs.

    People with lupus may first experience tiredness, joint pain or a little bit of rash（皮疹）on their bodies and can go for a long time before their doctors realize it is more serious. Many people see two or four doctors before the real problem is picked up. According to Dr. Kyriakos Kirou, roughly a third to one-half of people with lupus develop kidney disease, and up to one in five of them will eventually need a transplant, sometimes because they weren't treated with effective drugs to prevent the immune system from attacking the kidneys. Though Gomez said that she was “very well now,” she warned about the dangers of not taking medical diagnoses seriously, like she initially did.

    Her Instagram post also called attention to two major health topics: the need for living organ donators and the fact that Gomez represents three groups more likely to be diagnosed with lupus and lupus-related kidney disease. Nine out of 10 people diagnosed with lupus are women, and most develop the disease between the ages of 15 to 44. And lupus is two to three times more common among women of color, including Hispanic women, according to the Lupus Foundation.

    Raisa is Latina, and Gomez's father is of Mexican origin. While it's not essential that the organ donator and receiver be of the sane ethnicity, people who share a similar background sometimes are better matched, according to data from the United Network for Organ Sharing.

    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 exercise too little.

    I am fat because I burn calories slowly.

Wrong! Fatness is not caused by a slow metabolism (新陈代谢). If fact, although fat people consume more energy that 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 many times. The key is to develop a balanced and varied program 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 your body adapting to the positive changes in your lifestyle and the aches should disappear relatively quickly. If you don't, rest and seek medical advice.

    People generally like to pick out the best-looking fruits and vegetables when shopping for produce, but Canadian supermarket chain Loblaws is attracting customers with badly-shaped and imperfect produce at the price of 30% lower than normal-looking ones.

    A trial run of the ugly food line, named "Naturally Imperfect", began with only apples and tomatoes to choose from. Consumer(消费者) demand has been so huge that Loblaws is going to introduce more ugly vegetables and fruit like onions and mushrooms.

    All the produce that will be sold through Naturally Imperfect would otherwise have been used in juices, sauces, or soups, or have not been harvested at all. The director Dan Branson explained that this program benefited both food producers who would otherwise have to let abnormal produce go to waste, and consumers who could buy fresh produce at low prices. And he was right, considering how popular the line has become.

    "It really went well beyond our expectation," Branson said. "I think it really spoke to the fact that Canadians are out there really looking for some Choices."

    Of course, Canadians know that beauty is more than skin(外皮) deep, and they also recognize that they get the same flavor and nutritional (营养的) benefits in spite of appearances. The positive response to the offering of apples and potatoes showed the opportunity to expand the line and offer more choices at a greater price to Canadian families.

    "If you grow produce in your backyard, there will be a lot of produce that won't look as pretty as what you will see in a grocery store", said Branson. "And nature doesn't grow everything perfectly. I'd like to think if somebody were to take a NO Name Naturally Imperfect apple, put it right beside a No. 1 apple, close his eyes and eat them, there would be no difference."

Researchers believe they have found evidence for a hidden ocean on Mimas, one of Saturn's major moons. This makes Mimas a target for learning more about the origins of life in our solar system. 

Saturn has 146 moons orbiting it. The biggest is larger than the planet Mercury; the smallest is roughly the size of a sports field on the Earth. Mimas, which was first discovered in 1789, is one of the major moons and is about 250 miles wide. 

Experts used to think Mimas was mostly made out of solid ice and rock. In 2014, astronomers noticed its orbit around Saturn was moving unsteadily. A shaky orbit can be caused either by a core shaped like a rugby ball or a huge liquid ocean beneath the surface. At first, lots of astronomers argued against the suggestion that Mimas had an ocean because there is no sign of it on the surface. 

To investigate more thoroughly, researchers looked at images taken by Cassini, a NASA spacecraft sent to study Satun. The images showed that the moon's orbit around Saturn drifted by about six miles over 13 years. The team's calculations found that the only way Mimas could move in this way is if it had a hidden ocean under the surface. They think the ocean formed when the moon's core warmed up and melted some of the ice. 

Mimas is just one of many moons that scientists think could have oceans below the surface Ganymede, which orbits Jupiter and is the largest moon in the solar system, has more water in its ocean than all of the oceans on the Earth. Titan, another of Saturn's moons, is believed to have a salty ocean beneath the surface. 

Space agencies want to study these oceans because they might be home to living organisms. However, the ocean on Mimas might not be old enough for life to have emerged there yet. It took hundreds of millions of years for life to develop on the Earth and the ocean on Mimas is relatively young;it is less than 25 million years old.