Correct Answer - (d)
As the measured value is 3.50 cm, the least count must be = 0.01 cm = 0.1 mm For given screw gauge in option (a), least count `= (1 mm)/(100) = 0.01mm`
Least count in option (b) `= (1mm)/(50) = 0.02 mm`
Least count in option (c ) =1 mm
Least count in option (d) = 1 MSD - 1 VSD
`=1MSD - (9)/(10)MSD`
`=(1)/(10) MSD = (1)/(10)xx 1mm = 0.1 mm`
Thus vernier calliper is usedc for the measurement. Hence option (d) is true.