4．After reading the passage we know________.

　　A．at present rats have taken the place of dogs in searching for people

　　B．the"rat project" has been completed

　　C．people are now happy to see a rat in a building

　　D．now people still use dogs and robots in performing rescues

　　B

　　Most people prefer to stay indoors during a snowstorm, but Kenneth Libbrecht is not most people. When snow starts falling down from the winter sky, the scientist's work begins. Taking a magnifying glass(放大镜), a paintbrush, and a camera with him, he heads out into the cold.

　　Outside, Libbrecht waits for snowflakes(雪花)that are just right. Sometimes he waits for hours. Finally, he sees the snowflakes he's been waiting for. As the snowflakes fall, Libbrecht carefully catches them on his paintbrush. Then he points his camera and shoots.

　　The scientist's shiny pictures recently earned him a prize, which is given to top science photographers around the world.

　　Libbrecht takes pictures of snowflakes to learn more about their shapes. The snowflakes form when water steam(水蒸气) in a cloud freezes. Every snowflake grows into a hexagon. That is a six­sided shape. However, no two snowflakes look the same. Experts are not sure why.

　　To find the answer, Libbrecht has traveled to snowy places around the world. He has taken pictures of snowflakes in Canada, Alaska, and Vermont. The work takes patience, Libbrecht explained."It doesn't snow all the time, and when it does, the snowflakes aren't always good，" he said. Once he's collected enough pictures, he returns to his science lab in California to do research.

　　Since developing his interest in snowflakes, Libbrecht has collected nearly 10,000 snowflake pictures. He will spend most of this winter studying them. The scientist's outdoor work is far from over, though. Libbrecht plans to one day go to other snowy places to take more photos.

　　"I really enjoy watching the snow fall and trying to see what I can find，" he said."There is a lot of fun."

　　Kenneth Libbrecht also gave some good advice to kids who want to study snowflakes. "You don't need a lot of things. With a simple magnifying glass on a snowy day, you can really see quite a bit if you just stop and look."

　　5．Kenneth Libbrecht is different from most people in that________.

　　A．he likes to take pictures B．he likes to research snow

　　C．he doesn't like warm weather D．he doesn't like life indoors

　　6．Paragraph 2 is mainly about________.

　　A．how snow forms

B．what snowflakes look like