非谓语动词与独立主格：短语，句子（或者句子，短语）
1.当短语部分有独立主语，并且该主语不同于句子主语，这时短语结构称为独立主格。（它最明显的特点是短语部分有独立的主语）。
独立主格的结构1：名词（代词）+ 分词 [现在分词、过去分词]
现在分词表示主动的，正在进行的行为;过去分词表示被动的，已经完成的行为。 作题时要通过判断动作与名词（代词）之间的关系来确定是使用现在分词还是过去分词。当动作由名词（代词）发出时使用现在分词，而名词（代词）是受动者时则用过去分词。
54. silver is the best conductor of electricity， copper _b_ it closely.
a followed b following c to follow d being followed
49. all things _a_， the planned trip will have to be called off.
a considered b be considered c considering d having considered
call off 取消; cancel vt. 取消; 四级中的考点就是现在分词和过去分词的区别。
独立主格的结构2：with + 名词（代词）+ 分词 [句子当中作状语]
36. after the arab states won independence， great emphasis was laid on expanding education， with girls as well as boys _c_ to go to school.
a to be encouraged b been encouraged c being encouraged d be encouraged
as well as 和（相当于and）; be encouraged不会考。
动词不定式有预示将来行为的含义。to be encouraged 将要被鼓励;
been encouraged 已经被鼓励完了，与主句的谓语动词相对;being encouraged 正在被鼓励