so that既可引导目的状语从句,也可引导结果状语从句,可以由以下几点进行区分：
1.当表达“为了……”、“以便……”的含义时,引导的是目的状语从句；
当表达“以至于……”、“因此”的含义时,引导的是结果状语从句.如：
If you do know,answer in a loud enough voice so that all the class may hear.如果你的确知道,应大声回答,以便让全班同学都可以听见.
It rained hard the day before yesterday,so that she had to stay at home.前天雨下得很大,因此她只好呆在家里.
2.当从句的谓语动词有情态动词can,could,may,might,should等时,是目的状语从句；当从句里没有情态动词,且谓语动词是一般现在时、一般过去时或现在完成时等时态时,引导的是结果状语从句.如：
We stopped at Salt Lake City so that we could visit the monument to seagulls.我们在盐湖城逗留,为了可以参观为海鸥修的纪念碑.
They have walked a long distance so that they are all tired.他们走了很长的路,所以都很累.
3.当so that之前有逗号时,引导的是结果状语从句；反之,引导的是目的状语从句.如：
You didn’t plan your revision well,so that you didn’t pass the exam.你没有好好地按计划复习,结果你没考及格.
The teacher must speak slowly so that the students may understand him.那位老师必须讲得慢些,以便所有的学生可以理解.
