—This is my treat and next is yours． How's that?

—OK．         ．

A．It doesn't matter

B．It depends

C．No way

D．It's a deal

千分尺固定套筒上刻有间隔为0.5mm的刻线5，微分筒圆周上均匀刻有50格。微分筒每转一格，测微螺杆就移进（）mm。