题目内容：

    When the weather gets cold, we can put on more clothes, stay next to a fireplace, turn on the air conditioner or simply travel to a warmer city to spend the winter – people have many different ways of coping with the cold.

But things are not as easy for plants. Unlike humans, plants can’t move to escape the cold or generate heat to keep themselves warm. So how do they manage to survive the freezing winter?

It turns out that plants have their own strategies too, said a study published on Dec 22 in the journal Nature.

According to researcher Amy Zanne of George Washington University, US, the cold is a big challenge for plants. Their living tissues can be damaged when they freeze. “It’s like a plant’s equivalent to frostbite (冻疮),” Zanne told Science Daily. Also, the process of freezing and thawing (解冻) can cause air bubbles to form in the plant’s water transport system. “If enough of these air bubbles come together as water thaws they can block the flow of water from the roots to the leaves and kill the plant,” she explained.

To live through cold weather, plants have developed three traits, according to the study. Some plants, such as oak trees, avoid freezing damage by dropping their leaves before the winter chill sets in – effectively shutting off the flow of water between roots and leaves – and growing new leaves and water transport cells when the warm spring returns.

Other plants, pine trees for example, protect themselves by narrowing their water transport cells, which makes it easier for cells to travel among air bubbles.

The third strategy is also the most extreme – some plants die on the ground in winter and start growing as new plants from seeds when conditions get warmer.

However, the study also found that these smart strategies were developed very slowly – over millions of years of evolution. This leads scientists to worry that plants may not be able to deal with human-caused climate change, which has only started occurring over the past few decades.

Scientists are hoping that this study can help people find possible ways to save plants from the threat of climate change.

1.What is the article mainly about?

A.Why plants are not afraid of the winter chill.

B.The ways that plants survive cold weather.

C.Changes in plants’ water transport system in winter.

D.How plants evolve to keep up with climate change.

2.According to the article, if a plant freezes in the winter, ______.

A.it produces more living tissues to stay alive

B.its leaves quickly fall out and its roots begin to die

C.its water transport cells are narrowed

D.its water transport system could be blocked

3.How do oak trees usually survive the cold winters?

A.By dropping their leaves before winter.

B.By narrowing their water transport cells.

C.By widening their water transport cells.

D.By dropping seeds on the ground so that the new trees can grow in the spring.

4.What are scientists worried about when it comes to plants according to the article?

A.Plants may not be able to adapt to the increasingly cold climate.

B.Human activities might have a great impact on the pace of plants’ evolution.

C.Plants may not be able to evolve fast enough to adapt to human-caused climate change.

D.The strategies plants develop are not good enough to protect them against cold.