There are some students on the playground. A. run B. running C. to run

问题补充：

There are some students on the playground.

A. run B. running C. to run

答案：

解析：考察非谓语动词。句意：有一些学生在操场上跑。现在分词作状语表示主语正在进行的伴随性动作，结合语境可知选B