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。
1. Silver is the best conductor of electricity， copper _B_ it closely.
A followed B following C to follow D being followed
2. 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]
3. 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
短语部分没有独立主语，则短语结构称为非谓语动词。
非谓语动词的结构：分词(分词短语)
句子的主语决定非谓语动词中的分词是用主动还是被动形式。如果是句子的主语发出动作，则使用现在分词;如果动作不是由句子的主语发出，则使用过去分词。
1.No matter how frequently _A_， the works of Beethoven always attract large audiences.
A performed B performing C to be performed D being performed
perform vt. 表演，演出，演奏;
to be performed 将要被演奏; being performed 正在被演奏;
一些特殊的动词：
第一点：forget 忘记; [反义] remember 记得;
这两个词后加动词不定式表示将要进行的行为;这两个词后加动词ing形式表示已经做过的事情。
注意：动名词与现在分词形式一样，但含义不同。这两个词后加动词ing形式都是动名词。
forget to do sth. 忘记要去做某事; forget doing sth. 忘记做过某事;
remember to do sth. 记得要去做某事; remember doing sth. 记得做过某事;
2. I remember _B_ to help us if we ever got into trouble.
A once offering B him once offering C him to offer D to offer him
offer vt. 提出，提供; offer sb. sth. / offer to do sth.
him once offering 如果改成 his once offering 也正确。
