题目内容：

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.

1.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.

2.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.

3.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

4.What is the researchers’ attitude towards the future of the bristlecone pine?

A. Positive.    B. Concerned.

C. Enthusiastic.    D. Indifferent.