问题
选择题
—— I can’t get through to the general manager’s office anyhow.
—— The line is busy. Someone＿＿＿＿＿the telephone.
A．must use
B．uses
C．must have been using
D．must be using
答案
答案：D
must be using表示此刻“一定正在使用……”。