someday,some day,some days与 somedays的区别

题目

someday,some day,some days与 somedays的区别
理论讲解后,请看例题：（注意：要先讲下哦）
Life is changing and_____each of us may have a car.
a.some day b.some days
c.someday d.somedays

答案

答案是a吧 some day指某一天
生活总是变化的,某一天我们每个人都会有一辆车