to do sth is difficult
it is diffcult to do sth
it is diffcult for sb to do sth
it is diffcult for the average reader
under the forty age to image a time when
引导定语从句 什么样的时间
I came into the woods,I saw two birds.×
两套主谓宾 哪个是主干呢
I came into the woods and I saw two birds.
and 连接两个句子就不存在歧义。并列句 （一主一并)
when I came into the woods ， I saw two birds.（一主一从）
连词起连接和降级功能。
连词
并列
句子：主谓宾and主谓宾
词：词and 词不数
从属
when 主谓宾，主干
when doing sth ，主干.
doing sth是非谓语动词短语，不数
套用主干公式
连词/动词
一个连词 说明有一个从句/并列句
还说明有一个从句/并列句的谓语动词
当有n-1个连词，就有n-1个从句/并列句
有n-1个从句/并列句的谓语动词
当有n-1个连词 ，整句话谓语动词为n.
所以n-（n-1）＝1
2.谓语动词的3种时态
is do did doing to do done
动词时态变化表现在将来过去
时+态
时表过去现在将来
只有态没有时 叫非谓语动词
doing进行态
done完成被动态
to do不定态
时+态 叫谓语动词
态不变 时变
进行态doing
were/was doing
are/is doing
will be doing
完成态done
had done
have done
will be done
have largely done 副词修饰done
have in large part done 介词短语修饰done
一般态do
did+do＝did I loved you ＝I did love you.
do+do＝do
will do+do＝will do
Tom doing his homework.
doing只表示状态
谓语动词语态
be done 被动语态
be (状语)done
be largely done 副词修饰done
be in large part done 介词短语修饰done
3.情态动词+动原
can be/may be
be able to do
be able to＝can
be willing to do sth
be likely to do sth
have to do sth
