Question

—Why，I didn’t get you on the phone.
—We ________football on the playground when you phoned.

A．must be playing

B．must play

C．must have played

D．must have been playing

Answer 1

D
解析　句意为：——嗨，我打电话没找到你。——你打电话的时候我们肯定正在操场上踢足球。表示对过去所发生的事情的肯定推测用must have done的形式，再结合语境可知此处推测的是过去某个时间正在发生的事情，故用must have been doing，故答案为D项。