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Find Which Direction Is South

    Do you have a good sense of direction? If not, please take with you a compass. But if you forget to take a compass, you can still find your way. 

    It's never a wise idea to believe that the family member who was good at the job of map-reading knows where the family is. You can tell by the troubled look on their faces that nothing on the ground seems to match the map. Never mind. The sun is shining and it's still morning. If you don't know the exact time, you can still find out where south is, but you'll need to be patient. 

    ①Find a straight stick and put it in the ground in a place where you can mark its shadow(a dark shape on a surface that is made when something stands between a light and the surface). 

    ②Try to position the stick as vertically(垂直)as you can. You can check this by making a simple plumb line(铅锤线). You haven't got one? OK, use a thread(线) from your clothes with a button(纽扣) tied at the end to act as a weight.

    ③Mark the end of the shadow cast(投射) by the stick.

    ④Wait about half an hour and mark the end of the shadow again.

    ⑤Keep doing this until you have made several marks. 

    ⑥The mark nearest the stick will represent the shortest shadow, which is cast at midday, when the sun is highest in the sky and pointing to the exact south. 

    ⑦Pick a point in the distance along the line between the shortest shadow and the stick.

    ⑧That point is south of where you are. 

    ⑨Now you can turn the map, like you did before, and find which way you should be travelling. 

C

    Paul is a photographer(摄影师). He went to the Arctic to take pictures for NationalGeographic(《国家地理》). Finally, he saw a big and white polar bear swimming to him in the icy water.

    Paul lay down the ice to get a better photo, but the polar bear jumped out of the water and tried to attack him! Luckily for Paul, the ice cracked(破裂), or broke and the bear fell back into the water. The polar bear wasn't so lucky. It couldn't get a meal and had to swim farther away to find food.

    To understand the polar bear's problem, you need to know two things about the Arctic. First, the Arctic is mostly ocean(海洋). Second, ice covers(覆盖) a lot of the Arctic Ocean. In winter, the ice is thick, but in summer, the ice becomes thinner and breaks into pieces. Sea ice is the key to survival for Arctic animals. However, because of global warming, Arctic temperatures are rising and polar ice is melting(融化).

    Polar bears need ice  to hunt(捕捉) seals, their favourite meal. They stand on the ice and wait for the seals to come up for air. As Arctic ice melts, polar bears have to swim farther to find ice floes, or large pieces of floating ice. Sometimes, bears have to swim more than 200 km to find an ice floe. Some bears cannot swim that far and sadly they drown(淹死).

    On his last trip, Paul saw three dead bodies of polar bears. Before global warming threatened(威胁) Arctic ice, a dead bear was a rare sight. Paul is sad to see the dead bodies. Wildlife experts(专家) think global warming will have a terrible effect(影响) on polar bears. In the future, polar ice will continue to shrink and endanger the bears. Some scientists believe 65 percent of the world's polar bears will disappear(消失) by 2050. In other words, polar bears are in great danger.

    People and dogs have been living together for hundreds of years. When did dogs and people become friends? Where did dogs come from?

    A group of scientists tried to answer these questions. They just finished a study about the history of dogs. In the study, they looked at the DNA of dogs all over the world and found that dogs, like humans, shared DNA with their family members. The scientists put together a big family tree for dogs. It went all the way back to the animal's beginning.

    In this way, scientists learned about the history of dogs. The first dogs lived in Asia. They were born about 33,000 years ago. At first, there were only about 6,400 of them. Their parents were wolves(狼).

    The new study answers many questions. It raises some too. For example, what caused wolves in Asia to become dogs all those years ago?

    One idea is that their DNA slowly changed and the wolves became dogs in the end. As time goes by, dogs became "man's best friends" Or it could happen the other way around. It was possible that some wolves started living with people before they became dogs. Living with people led to many changes to these wolves. It changed their DNA, so their offspring(后代) became dogs. In other words, it was possible that wolves were our friends before they became dogs.

    By studying DNA, scientists now have a much better understanding of the history of dogs. ________.

    How exactly dogs came to be our friends is still unclear.

I am Nancy, and my brother is Bob. {#blank#}1{#/blank#}

 In my room, my books and dictionaries are in the bookcase. Where are my keys? {#blank#}2{#/blank#} I havea black schoolbag. It is on the chair. My pens, pencils and erasers are in my pencil box. {#blank#}3{#/blank#}

 In Bob's room, his books and notebooks are everywhere— on his bed and his chair. He has a tape player. {#blank#}4{#/blank#} It's under his bed. And his schoolbag is under his bed, too. Bob always asks," Where are my keys? Where's my ruler? Where's my pen?"{#blank#}5{#/blank#}

Friends are very important in everyone's life because friends are always there when we need them. It's great to have many friends and I can't think about my life without my friends.

My best friend is Lisa. When I first met her, I was five. She is one year older than me. Now she is in the same class with me. In the seventh grade, she is tall and quite thin. She has long curly blonde hair and blue eyes. I am not so beautiful. Sometimes I wish I could be as beautiful as she is.

My name is Molly. I am tall enough but little fat. Lisa and I like doing a lot of things together and talking about different things. She always helps me with my math and I sometimes help her with her English and history. I have to do a report(报告) on science, but I didn't understand what the teacher said. The next day I read it in front of the class, but the teacher told me that my report was wrong and all my classmates laughed at me. I felt very bad about myself. Lisa was the only one who didn't laugh at me. She tried to be nicer than anybody else and make me happy.

I am a shy person and sometimes I feel that people don't understand me. Lisa is friendly and everybody loves her. She is also smart and she can deal with (解决) everything. I am happy to have a friend like her.