I wonder what Sam _____ (do) at the moment.Let me call him.快,有理由说明!

问题描述:

I wonder what Sam _____ (do) at the moment.Let me call him.快,有理由说明!

I wonder what Sam _is doing____ (do) at the moment.Let me call him.
句子意思是“我想知道山姆现在正在做什么.我来给他打个电话.”
因为是要打电话问正在做什么,所以动词要用现在进行时,就用is doing