Screw gauge shown in the figure has 50 divisions on its circular scale and in one complete rotation of circular scale the main scale moves by 0.5 mm. The diameter of a sphere is measured using this screw gauge. Two positions of screw gauge are shown in the figure. The diameter of sphere is [IIT-JEE 2006] PQ (a) 1.25 mm (b) 1.20 mm (c) 2.25 mm (d) 2.20 mm