都可以,但是含义各不相同。1. on the playground是最常用的,强调“在操场的表面上”。如:The students are palying soccer on the playground.2. at the playground比较少用,只表示“在操场那个地方”,有时可以和on the playground换用,强调“操场是个小地方”。3. in the playground强调“在操场表面的地里面”。如:There is a hole in the playground.在操场里有一个坑。注:最常用的是on the playground,除非是强调“在操场地表里面”时用in the playgro...