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　句意為：——嗨，我打電話沒找到你。——你打電話的時候我們肯定正在操場上踢足球。表示對過去所發生的事情的肯定推測用must have done的形式，再結合語境可知此處推測的是過去某個時間正在發生的事情，故用must have been doing，故答案為D項。