2012年托福考试语法辅导：现在分词_第2页

2. 现在分词作状语
　　分词还可在句中作状语，可放在句首、句中或句尾。现在分词作状语时，通常都表示主语正在进行的动作/伴随动作或者表示原因。
　　1．现在分词短语可以作时间状语，相当于when, while, as soon as等所引导的从句
　　如：Hearing the news, he couldn’t help crying.
　　= When he heard the news, he couldn’t help crying.
　　2．现在分词短语也可以表示原因，代替由since, as等所引导的从句
　　如：Not knowing what to do about the situation, she turned to him for help.
　　=Since she didn’t know what to do about the situation, she turned to him for help.
　　Being so poor in those days, we couldn’t afford to go to school.
　　=As we were so poor in those days, we couldn’t afford to go to school.
　　3．如果分词表示的动作发生在主句动作之前，那么此时分词就需要用完成形式
　　如：Having finished the work, she went to the park.
　　=After she had finished the work, she went to the park.
　　特别注意：分词状语的逻辑主语和句子的主语要保持一致
　　如: Seeing from the moutain, the ocean is emrald green.
　　此句是一个错误的句子, 因为根据分词状语的逻辑主语和句子的主语要保持一致的原则, seeing的逻辑主语也应该是the ocean, 而the ocean是不能自己seeing的, 应改为Seen from the mountain.
　　例题：
　　(1)
　　Snow aids farmers by keeping heat in the lower ground levels, thereby ---- from freezing.
　　(A) to save the seeds
　　(B) saving the seeds
　　(C) which saves the seeds
　　(D) the seeds saved
　　答案：B
　　解释：thereby一词习惯上接现在分词作句子的结果状语，只有B符合要求