66　狀語從句的簡化　Track64

只有當(dāng)狀語從句的主語和主句的主語相同時(shí)，才能把狀語從句換成短語。 否則，會(huì)引起句意改變。
While the teacher was lecturing to the class, I fell asleep.
在老師講課的時(shí)候，我睡著了。
若改成“While lecturing to the class, I fell asleep.”，則意思是“當(dāng)我在給這個(gè)班上課時(shí)，我睡著了。”這樣顯然不妥。
（1）從句含有be動(dòng)詞
如果狀語從句中含有be動(dòng)詞的形式，我們只需要把從句主語和be動(dòng)詞省去，即簡化成短語。簡化后的短語往往是分詞短語（主動(dòng)的用現(xiàn)在分詞，被動(dòng)的用過去分詞）、形容詞短語或名詞短語。這種省略主要常見于時(shí)間、地點(diǎn)、條件及讓步狀語從句中。
a.Metals expand when (they are) heated and contract when (they are) cooled . 金屬具有熱脹冷縮的特性。（兩個(gè)when后省略they are）
b. When (he was) a student in the university, he read a lot.（when后省略了he was）
c. While (he was) waiting , he took out a magazine to read.
d.A tiger can't be tamed unless (it is) caught very young.
e._________, Dr. Smith has long been a severe critic of the govern-ment's economic policies.
A. Although not being an economist himself
B. Although not an economist himself
C. Although not having been an economist himself
D. Although being no an economist himself
正確答案：B。從句相當(dāng)于：Although he is not an economist himself, ...
（2）從句沒有be動(dòng)詞
如果狀語從句中沒有be動(dòng)詞的形式，我們則可以把從句主語省去并且把動(dòng)詞變成現(xiàn)在分詞-ing形式。