B．protect themselves against insects

　　　C．talk to one another intentionally

　　　D．help their neighbors when necessary

　　　11．What can we infer from the last paragraph?

　　　A．The world is changing faster than ever.

　　　B．People have stronger senses than before

　　　C．The world is more complex than it seems

　　　D．People in Darwin's time were imaginative.

　　　The bristlecone pine is the longest-living thing on the earth. These trees, with their strangely-shaped, wind-beaten limbs(枝干), can live up to 5,000 years. But experts worry that a warming climate in some areas may threaten its future.

　　　Researchers say warmer weather is permitting a similar kind of tree, the limber pine, to take over good growing places from the ancient bristlecone. They say the tree is being crowded out of mountainous areas where it grows.

　　　"The bristlecone pine is the oldest individually growing organism," researchers say. They grow in high mountain forests in eastern California, Nevada and Utah. In those mountains, the trees face high winds and extreme temperatures, which leave them with twisted limbs and shapes. "Even in such tough conditions," Brian Smithers, a researcher at the University of California, said, "the limber pine is taking all the good spots."

　　　The limber pine is the bristlecone's distant relative and competitor. It can also live a long time--up to 2,000 years. And it is usually found at lower altitudes, where temperatures are warmer. However, according to a three-year study which centered on trees that have started growing in the last 50 years in California's White Mountains, most of the trees growing at higher altitudes were limber pines.

　　　Scientists compared the competing species to two o1d men in a very slow race up a mountainside. This race between such slow-growing trees takes thousands of years. They say climate change is causing the competition.

　　　Smithers said the bristlecone pines are not in danger of disappearing. But he assumes they could be crowded out of some places where they have grown for thousands of years.

　　　The researchers say the findings show how climate change can affect the two kinds of trees. The information, they say, can help scientists understand more complex forests.

　　　12．What's the function of Paragraph 1?

　　　A．To introduce a topic. B．To summarize the whole passage.

　　　C．To describe the appearance of a tree. D．To praise the hard work of the experts.

　　　13．What does the underlined sentence in Paragraph 2 mean?

　　　A．There will be older trees sent out of those mountains.

　　　B．There will be more places covered with bristlecone pines.

　　　C．There will be better limber pines replacing the ancient ones.

　　　D．There will be fewer bristlecone pines growing in those areas.

　　　14．According to the passage, the reason why limber pines can grow at higher altitudes is_________.

　　　A．the high winds B．the difficult conditions

　　　C．the changing climate D．the extreme temperatures

　　　15．What is the researchers' attitude towards the future of the bristlecone pine?

　　　A．Positive. B．Concerned.

　　　C．Enthusiastic. D．Indifferent.

二、七选五

　　　While many people are physically active in high school, there are always many things for teens to compromise their healthy lifestyle.16．

　　　Get plenty of rest. With homework and social commitments, teens in high school have a tendency to stay up late and rise early.17．Then go to sleep early enough, turn off the television or radio and unplug the phone to prevent your sleep from being disturbed.

　　　18．Teens are well-known for living on a diet of junk food and soda. Drink plenty of water and eat whole grains and vegetables daily. If you mainly eat nutritious foods, the occasional fast food hamburger or late night pizza won't hurt you.

　　　Say no to cigarettes and alcohol. Lifelong habits start during high school years, so make sure the habits you are forming are good ones. Getting hooked on cigarettes and alcohol at a young age can lead to an adulthood spent battling addictive habits. 19．

　　　Exercise regularly. Physical activity helps build a strong body and mind. Teens who exercise throughout high school benefit from a healthy body and a mind that is more at ease with less stress.

　　　Share with friends and family.20．A healthy teen will find someone to talk with about their problems rather than dealing with them alone or not dealing with them at all. If you can't trust your parents, turn to your friends or teachers when you are upset or stressed out.

　　　A.Eat a well-balanced diet.

B.Motivate yourself to study harder than before.