If a bearing is designated by the number 305, it means that the bearing is of
(a) light series whose bore is 5 mm
(b) light series whose bore is 25 mm
(c) medium series whose bore is 5 mm
(d) medium series whose bore is 25 mm
(a) light series whose bore is 5 mm
(b) light series whose bore is 25 mm
(c) medium series whose bore is 5 mm
(d) medium series whose bore is 25 mm