题目内容：

    Pycnandra acuminate (喜树) is a rare tree native to New Caledonia that has the rare ability to collect heavy metals like nickel (镍) from the ground. The liquid circulated in its body is blue-green and reportedly contains up to 25% nickel.

In general, trees and heavy metals like nickel don’t really go well together. But Pycnandra acuminata make them live together. And that’s what makes Pycnandra acuminata so special. It sucks out normally poisonous levels of heavy metals from the soil and store them in its trunk, leaves and seeds.

The evolution of Pycnandra acuminate is believed to have occurred over millions of years, but scientists have yet to identify a universal principle of nickel intake and storage. The reason why such trees have formed the way of absorbing metals is also up for debate.

The most popular theory states that the concentration of nickel protects such trees from leaf-chewing insects. And studies have shown that nickel accumulated by these trees indeed harms many insects though some have developed a high tolerance to it. Another theory says nickel has effects of resisting bacteria, which protects the trees from various diseases. However, these theories are all just theories.

One thing that has been proven is the ability of Pycnandra acurninata to clean the soil with poisonous materials caused by human activity. There’s also clear potential for collecting heavy materials like nickel in these kinds of soils that will bring a few profits by conventional ways of mining. People can collect minerals contained in such soils from the blue-green trees。

Unfortunately, Pycnandra acuminata is is recently in a bad situation. Human activity in forests of New Caledonia has made Pycnandra acuminata in danger. Consequently, probably fewer than several hundred trees of this kind have remained as a result of the reduction of our forests.

1.What do we know about Pycnandra acuminata?

A.It has a blue-green color due to metals collected.

B.It is able to collect some heavy metals from the ground.

C.It sucks out a great deal of poisonous underground water.

D.It tends to grow in the soil with plenty of poisonous liquid.

2.What do the theories in paragraph 4 say about Pycnandra acuminata?

A.It indeed protects many insects.

B.It stores most nickel in its roots.

C.It protects itself through the concentration of nickel.

D.It makes its surrounding plants suffer from diseases.

3.What does the author mainly want to express in the last paragraph?

A.Pycnandra acuminata is in danger.

B.Forests are to blame for the reduction of trees.

C.Forests are decreasing as a result of human activity.

D.Pycnandra acuminata is under the protection of people.

4.In which section of a magazine is this next most likely to appear?

A.Bacteria and disease. B.Health and life.

C.Fashion and entertainment. D.Man and nature.