---- I can’t get through to the general manager’s office anyhow. ---- The line i

---- I can’t get through to the generalmanager’s office anyhow.

   ---- The line is busy. Someone ___________ thetelephone.

   A. can have used       B. canuse

   C. must have used      D. must beusing

试题答案

【答案】

D

【解析】

试题