这句话哪个是谓语动词哪个是主语啊~
theirmigrationmayhavebeensetupinmotionbyanincreaseinpopulationcausedbyamovementofpeoplefleeingthedesiccation,ordrying,oftheSahara.
如果一句长难句怎么才能很快的找出谓语动词和主语~