一.一.结构结构 :to do to do(否定否定)not/never to do)not/never to do省略省略toto的的:do:do三三.用法用法/功能功能To see is to believe.Its important to learn.(1).主语主语不定式作主语时不定式作主语时,往往放在谓语之后往往放在谓语之后,用用it作形式主语作形式主语.To learn a foreign language is not easy.=Its not easy to learn a foreign language.Its+(for+sb.)+to do sth.Its+difficult,hard,easy,possible,impossibleImportant+(of+sb.)+to do sth.clever,wise,kind,good,right,nicewrong,bad,cruel silly,stupid,foolish careful,carelesse.g It is hard _ you to do it well.=For you to do it
