（2）连词so that, in order that可以引导目的状语从句。当主句用一般现在时、现在完成时或一般将来时的时候，so that和 in order that后面可以跟may, can或will。so that比in order that更为普遍：I've arrived early so that/in order that I may/can/will get the tickets.我到得早，以便能买到票。

当主句中的动词为一般过去时、过去进行时或过去完成时的时候，so that和in order that后面跟should, could, might或would：I arrived early so that/in order that I should/could/might/would get the tickets.我到得早，以便能买到票。

so that和in order that后面的否定形式如下：I arrived early so that/in order that I might not miss anything.我到得很早，以免错过什么。（否定句中不可用could,可用should, would等）

（3）相比之下，带to, so as to和 in order to的结构比带that的结构要简单、自然，所以多为人使用：I arrived early so as not to/in order not to miss anything.我到得很早，以免错过什么。

当前后主语不一致时，不定式前面加for 名词/代词比that结构更简洁。