Which one of the following instruments is widely used to check and calibrate geometric features of machine tools during their assembly?

For machining a rectangular island represented by coordinates
$$P(0,0), Q(100,0), R(100,50)$$ and $$S(0,50)$$ on a casting using $$CNC$$ milling machine, an end mill with a diameter of $$16$$ $$mm$$ is used. The trajectory of the cutter center to machine the island $$PQRS$$ is

For the given assembly : $$25$$ $$H7/g8,$$ match Group $$A$$ with Group $$B$$

A metallic rod of $$500$$mm length and $$50$$mm diameter, when subjected to a tensile force of $$100$$kN at the ends, experiences an increase in its length by $$0.5$$mm and a reduction in its diameter by $$0.015$$mm. The Poisson's ratio of the rod material is _______ .