【单选题】
设计一孔,其基本尺寸为∮50mm,最大极限尺寸为∮50.048mm,最小极限尺寸为∮50.009mm,则孔的上、下偏差为()。
A、﹢0.048mm ﹢0.009mm
B、﹢0.009mm ﹢0.048mm
C、﹣0.048mm ﹣0.009mm
D、﹣0.009mm ﹣0.048mm
A、﹢0.048mm ﹢0.009mm
B、﹢0.009mm ﹢0.048mm
C、﹣0.048mm ﹣0.009mm
D、﹣0.009mm ﹣0.048mm