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      Earth has warmed by about 1ºF over the past 100 years. But why? And __1__ ? Well, scientists are not exactly sure. The Earth could be getting warmer on its own, __2__ many of the world’s leading climate scientists think that things people do are helping to make the Earth warmer. Global warming refers to an average increase in the Earth’s temperature, __3__ in turn causes changes in climate. A __4__ Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans. When scientists talk about the issue of climate change, their __5__ is about global warming caused by human activities. It is because they are sure about the danger of the green houseeffect.

文意解析：

 Earth has warmed by about 1ºF over the past 100 years. But why? And __1__ ? (地球暖化比過去的100年超過華氏1度。但是為什麼呢？又是如何形成的呢？)

 1、

 (A)quick 快速。

 (B)now 現在。

 (C)how 如何。 

(D)where 何時。

 因為是問句，所以先刪除(A)(B)。

 由後句的回答，可知不是在問地點，所以答案為(C) how (如何形成的？)。

Well, scientists are not exactly sure. (嗯...，科學家們也不太肯定。)

 The Earth could be getting warmer on its own, __2__ many of the world's leading climate scientists think that things people do are helping to make the Earth warmer. (地球本身自己會越來越暖，但許多世界的權威級氣候科學家們認為，人們所做的事情正在幫助地球變暖。)

 2、(A)but (B)so (C)or (D)for

 前後句子意思不相同，所以連接詞用 (A) but。

Global warming refers to an average increase in the Earth's temperature, __3__ in turn causes changes in climate. (全球變暖是指地球平均溫度增加，反過來又導致氣候變化。)

3、(A)and (B)it (C)not (D)which

※ in turn ，一般解釋為「依序」，但這裡解釋為「反過來又，相對地」。

In turn 當作「反過來又」時，前後可用標點符號隔開，也可以省略。但隔開後，更容易明白空格內要填入「連接詞+主詞」。

which in turn cause changes in climate

= which, in turn, cause changes in climate

如果用(A) and 必須改為「and it」，it 指的是 Global warming。

所以只能選(D) which ，關係代名詞兼具連接詞及代名詞雙重用法。

A __4__ Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans. (地球越暖和可能導致降雨分布改變，海平面上升，以及對植物，野生動物和人類的廣泛影響。)

4、

(A)crowded 擁擠的。

(B)flat 平面的。

(C)round 圓的

(D)warmer 越溫暖的

When scientists talk about the issue of climate change, their __5__ is about global warming caused by human activities. (當科學家們談論氣候變遷問題時，他們擔心的是人類活動引起的全球變暖。)

It is because they are sure about the danger of the green house effect. (這正是因為他們肯定溫室效應的危險性。)

5、

(A)story 故事。

(B)increase 增加。

(C)climate 氣候。

(D)concern 擔心。