There are lots of students___(play)ball games on the playground .

问题描述:

There are lots of students___(play)ball games on the playground .

playing

there are sb doing sth 某些人正在做某事

There are lots of students【playing】ball games on the playground .
固定句型:There be ……doing sth .表示 有……正在做某事.
本句意思是:有许多学生正在操场上打球.