— I can’t get through to the general man
题型：选择题
问题：
— I can’t get through to the general manager’s office.
—The line is busy. Someone ________ the telephone.
A．must have used
B．could use
C．could have used
D．must be using
— I can’t get through to the general manager’s office.
—The line is busy. Someone ________ the telephone.
A．must have used
B．could use
C．could have used
D．must be using