--- Where is Bob？He asked me to go swimming this evening.

--- Maybe he ________ in the bedroom now.

A. is swimming         

B. is watching  TV         

C. is camping

关于改善咬入条件，下列说法正确的是（）。

A．压下量一定时，增大辊径，容易咬入

B．减小轧辊摩擦系数，容易咬入

C．辊径一定时，加大压下量，容易咬入

D．以上说法都不对