A microscope is focussed on the scratch at the bottom of a beaker. Water is pured into it and the microscope is focussed again on the scratch at the bottom of the beaker. Some lycopodium power is sprinkled on the surface of water and microscope is focussed on to the powder. The corresponding readings are 1.17, 2.02 and 4.57 cm respectively, the refractive index of water is
A. `(3)/(2)`
B. `(3.4)/(2.5)`
C. `(4)/(5)`
D. `(3)/(4)`
