－Is it your boss in the office? 　

－No, it _____ be him. He has gone to Beijing on business. [ ]

A. mustn't

B. shouldn't

C. can't

D. needn't

下列关于仲裁开庭的说法正确的是( )。

A．仲裁应当开庭进行，当事人也可以协议不开庭

B．仲裁应当不开庭进行，当事人也可以协议开庭

C．仲裁不公开进行，当事人协议公开的必须公开

D．仲裁公开进行，当事人可以协议不公开