There are a lot of boys _____(play)volleyball on the playground.用括号内所给词的适当形式填空.

问题描述:

There are a lot of boys _____(play)volleyball on the playground.用括号内所给词的适当形式填空.
如果填出来了,请给个语法解释,为什么这样填.

应该用 Playing
因为根据语境应该是现在进行时,
所以,动词应该用ing形式~