so that 何时是“为了”,何时是“以至于”?

题目

so that 何时是“为了”,何时是“以至于”?
so that 既可以引导目的状语,“为了”；又可以引导结果状语,“以至于”.请问如何区分出两者?需要例句.

答案

1 so that
引导目的状语从句时,表示“以便；为了”,从句中常使用can /could /may /might /will /would /should等情态动词或助动词；引导结果状语从句时,从句中一般不用can和may等词,在so that前可以用逗号,意思是“因此;所以”.如：The little boy saved every coin so that he could buy his mother a present on Mother's day.
2 so ...that ..
so＋形容词或副词＋that ...引导结果状语从句.意思是“如此……以致于……”.如：When the football fans saw Beckham,they got so excited that they cried out.