Question

It’s a sure sign that summer is over and winter is on the way — leaves that were once deep green turn red, yellow and bright orange. It happens every autumn. But did you ever wonder why?

The leaves start changing color when the nights start getting longer and the temperature starts getting cooler. Some scientists think that as the number of daylight hours shrinks, the leaves stop making chlorophyll which makes plants green. The reason is that the process of making chlorophyll requires sunlight. But according to horticulture (園藝) educator Susan Rose from Colorado State University, it turns out leaves don’t really change color at all. “The fall colors are actually there all along,” she said. “But they are covered by the green chlorophyll. As the chlorophyll stops being produced, the other colors can shine through.”

The kind of color that the leaves are going to change to is determined by the plant’s genetic (基因的) background. In some places, the leaves start changing color in September — before autumn even officially begins. In other places, they don’t change until late October or even November. Some scientists say the leaves have been changing color later than usual in recent years. And they think global warming has something to do with that.

In one study, researchers found that the growing season in the Northern Hemisphere was nearly a week longer, on average, in 2008 than it was in 1982. And a professor from Harvard University found that the leaves, west of Boston, Massachusetts, are changing color about three days later than they used to. However, other scientists disagree with the global warming theory. Susan Rose said the leaves in her part of Colorado are changing “right on schedule.” But the leaves in other parts of that state are running a little late. “The lateness in the mountains may have something to do with the really warm late summer and early fall,” she said. “But I’m afraid that’s just a guess.”

1.According to Susan Rose, _____.

A．the fall colors are always in leaves

B．leaves make chlorophyll all the seasons

C．leaves’ changing color have nothing to with the weather

D．leaves begin changing color because they start making chlorophyll

2.The underlined word “shrinks” in Paragraph 2 could best be replaced by _____.

A．reduces          B．increases          C．lasts              D．a(chǎn)ppears

3.Scientists guess leaves change color later than usual probably as a result of _____.

A．genetic background                     B．dry weather

C．global warming                         D．low temperature

4.The purpose of the last paragraph is to tell readers _____.

A．why leaves change color at fall

B．leaves change color at different time

C．the effects of the global warming on plants

D．different opinions on the lateness of leaves’ changing color

 

Answer 1

【答案】

1.A

2.A

3.C

4.D

【解析】

試題分析：文章介紹秋天樹葉變顏色的原因，還有現(xiàn)在樹葉變綠的時間比以前遲了，科學(xué)家認(rèn)為主要是因為全球氣溫變暖造成的，還有科學(xué)家給出不同的解釋。

1.細(xì)節(jié)題:從第二段的句子：“The fall colors are actually there all along,” she said. “But they are covered by the green chlorophyll. 可知秋天的顏色一直在樹葉里面。選A

2.猜詞題：從后面的句子：the leaves stop making chlorophyll which makes plants green. 可知白天時間減少后，樹葉就不再產(chǎn)生會使樹變綠的chlorophyll ，選A

3.細(xì)節(jié)題：從第三段的句子：And they think global warming has something to do with that.可知科學(xué)家認(rèn)為現(xiàn)在樹葉變綠的時間比以前遲了，主要是因為全球氣溫變暖造成的。選C

4.細(xì)節(jié)題：從最后一段的句子：“The lateness in the mountains may have something to do with the really warm late summer and early fall,”可知最后一段是給出關(guān)于樹葉變顏色推遲的不同解釋，選D

考點：考查科普類短文

點評：本文屬于科普文章，介紹秋天樹葉變顏色的原因，還有現(xiàn)在樹葉變綠的時間比以前遲了，科學(xué)家認(rèn)為主要是因為全球氣溫變暖造成的，還有科學(xué)家給出不同的解釋。細(xì)節(jié)題居多，答題時在文章找到對應(yīng)的地方，用筆進(jìn)行標(biāo)記，這有利于后期有時間檢查時可以立刻找到答案的位置。仔細(xì)理解作者所講的意思，再結(jié)合選項，通過排除法和自己對全文的把握，選出正確答案。