考点二 过去分词
1. 过去分词作定语
与现在分词类似，过去分词作定语常可和定语从句替换, 通常表示被动的含义.
如：a theory derived from rich experience
= a theory that has been derived from rich experience
a gas composed of four chemical elements
= a gas that is composed of four chemical elements
单个分词可放在被修饰词之前，如：distinguished guests, unexpected trouble
改错题中常考现在分词和过去分词的混用，关键看被修饰词和分词代表的动作是主动还是被动关系。
例如: boiling water (沸腾的水，表示正在沸腾)； boiled water(开水， 表示已经烧开)
2. 同源现在分词和过去分词做定语的区别
有时一个动词词尾分别加上-ing和-ed就构成了一组同源现在分词和过去分词, 这样的例子在英语里很多, 如: interesting/interested, exciting/excited, disappointing/disappointed等, 这些由动词变化而来的分词已经被人们视为形容词了. 但是, 同源现在分词和过去分词做定语时有什么区别呢?
现在分词通常表示某个事物的特性, 通常用来修饰某事或某物, 含有“使人(令人)感到…”的意思, 如: an interesting novel, a confusing question等;
过去分词通常表示人的感受或状态, 意思是“…的…”, 如: a worried look (焦虑的神情)
试比较: an interesting boy (一个有趣的男孩 - 让人觉得很有趣)
an interested boy (一个产生了兴趣的男孩
同样, 当同源现在分词和过去分词做表语时, 在意思上也存在同样的区别, 如:
The results are very disappointing. (结果很让人失望)
We are very disappointed at the results. (我们对这样的结果很失望)
例题：
(1)
The University of Georgia, ----in 1785, was the first state supported university in the United States.
(A) chartered
(B) was chartered
(C) it was chartered
(D) to be chartered
答案：A
解释：本句主谓结构完整, 缺少的是主语的修饰成分, A构成过去分词短语作定语；B C 的动词结构与原句谓语冲突; D 不定式一般表示即将发生的动作, 与in 1785不符
(2)
A patent gives inventors exclusive rights to their inventions for a fix period of time.
应改为：fixed
解释：fix是动词，不能修饰名词period, 依句意改为分词fixed, “一段固定时间”
(3)
Closed plane figures like the square or the equilateral triangle can be grouped into a class ----polygons.
(A) called
(B) to call
(C) is called
(D) call as
答案：A
解释：此句主谓完整, 句中又无连词, 需填的只可能是非谓语成分, A 是过去分词短语作定语, 等效于which is called, 符合题意. C D 属谓语结构, 与原句谓语冲突; B 不定式表用途或目的, 意思不通
3. 过去分词作状语
过去分词也可放在句首、句中、句尾作句子的状语，常表示事件发生的背景或原因，
如：Seen from far away, the islands look like a chain of pearls in the midst of the lake.
Defeated in the final, the team gathered to analyze its technical disadvantages.
特别注意：分词状语的逻辑主语和句子的主语要保持一致. 选择题中, 经常要求考生在分词状语部分填入合适的过去分词或现在分词. 到底选择哪种分词, 考生可以采取这样的作题方法: 首先根据“分词状语的逻辑主语和句子的主语要保持一致”的原则确定状语部分的主语, 再判断这个主语和分词是什么关系, 若是主动关系则应该用现在分词, 若是被动关系则要用过去分词.
例题：
(1)
---- in 1635, the Boston Latin School is the oldest public school in the United States.
(A) Founded
(B) Founding
(C) To found
(D) Having founded
答案：A
解释：分词部分的逻辑主语也应当是the Boston Latin School, 它和found之间是被动关系, 所以空格处应填入过去分词
(2)
Almost destroy by fire in 1814, the White House was rebuilt and enlarged over the next three year.
应改为：Almost destroyed
解释：by是被动式的标志词, 动词destroy应用过去分词destroyed, 这样既表被动又构成句子的状语