题目内容：

    When we see babies or pets, we can't help gently touching them to show our love. And they give us happy feelings back. But a recent study shows that it’s different for plants.

A study, published in The Plant Journal, shows that plants don’t like to be touched. That’s because touching changes their genes(基因) and, even worse, can slow their growth. Professor Jim Whelan in Australia gave an explanation. The lightest touch from a human, animal, insect, or even plants touching each other in the wind, leads to a huge gene change in the plant.

In order to test the theory, the scientists did an experiment on plants. They grew a number of plants to the age of four weeks. Then they touched them with a paintbrush every 12 hours over a 36-hour period. They found that as the result of the touch, the mitochondria(线粒体) in the plants had been partly destroyed. The mitochondria are the “power-house” of the cell(细胞). The mitochondria produce energy for the cells in both animals and plants. If this “power-house” is weakened, the plants will lose a large amount of energy that should have supported their growth.

Whelan further explained, “If the touching is repeated, then plant growth is reduced by 30 percent.” Although the touching does have a strong influence on plants, usually the plants can still be alive. Touching changes the plants, but it’s not always a bad change. Continually touching or moving plants will make them grow shorter than other ones. However, in some ways, this change could be helpful. It may help plants fight threats to their health such as insects and bad weather.

The new research findings have led to a deeper understanding of the plants. And the research might help with the growth of plants.

根据材料内容选出最佳答案。

1.According to the article, what can get in the way of plants’ growth?

A.Love. B.Touch. C.Water. D.Weather.

2.How do the mitochondria support the plants’ growth?

A.By providing energy for cells. B.By changing the plants’ genes.

C.By fighting against the insects. D.By reducing the amount of cells.

3.Why did the scientists do the experiment?

A.To explain why pets love to be touched.

B.To find out why some plants grow more slowly.

C.To test if touching can change the genes of plants.

D.To show that plants’ and animals’ genes are different.

4.What does the underlined word “threats” mean in Chinese?

A.因素 B.改变 C.威胁 D.对手

5.What can we learn from the text?

A.Touching can have a good influence on plants’ growth.

B.We’re not sure how to help plants grow by touching.

C.It’s necessary to avoid touching the plants all the time.

D.The changes of the plants by touching may be not bad.