不定式可以表示目的状语,直接用【to do 】表示.
其强调形式有：
so as to do (只能放在句中,不能位于句首)
in order to do(及可以放在句首,也可位于句中)
例如：
We started early 【to catch 】the first bus to the Great Wall.
=【In order to catch】 the first bus to the Great Wall,we started early.
=We started early 【so as to/in order to catch】 the first bus to the Great Wall.
=We started early 【so that/in order that we could】 catch the first bus to the Great Wall.
*so that/ in order that(引导目的状语从句)