When circular scale of a srew gauge carrying `100` divisions is given four complete rotations, the head of the screw moves through `2mm`. The pitch and least count of screw gauge are respectively.
A. `1mm` and `0.005mm`
B. `0.5mm` and `0.001mm`
C. `0.5mm` and `0.005mm`
D. `0.005mm` and `0.005mm`