这句话哪个是谓语动词哪个是主语啊~

题目

这句话哪个是谓语动词哪个是主语啊~
their migration may have been set up in motion by an increase in population caused by a movement of people fleeing the desiccation,or drying,of the Sahara.
如果一句长难句怎么才能很快的找出谓语动词 和 主语~

答案

主语:their migration
谓语:have been set up
要点在于:先找谓语,最符合句子时态的以及相互间逻辑关系的动词,即为谓语.
例如这句,先找出可能作谓语的成分:have been set up ,caused.(fleeing以及并列的drying是分词,不可能作谓语).然后,此句无并列句,不可能同时作谓语,只能选其一.若后者做谓语,则前者成分无法解释;而前者作谓语,后者做定语即可.就是这样