轮流问你的同伴他或她喜欢在三明治里放什么.
这是祈使句,省略了主语you（你们）.
You take turns asking your partner what he or she like in sandwich.
take turn还是take turns
可以从单复数理解,两个都是轮流的意思,TAKE TURNS 多人轮流做某事,TAKE TURN 轮到某人做某事.
take turns替换,轮流
Susan and her brother take turns (at) doing the dishes.
苏珊和她的兄弟轮流洗盘子.
The students took turns to clean up their classroom.
学生们轮流打扫教室.
take turn :Please take your turn to play.轮到你去玩了.那为什么 要用asking ,动名词形式呢asking动名词作宾语补语，起到对turns的补充说明