In an experiment to trace the path of a ray of light passing through a rectangular glass slab, four students tabulated their observation as given below.

The student most likely to have done the experiment properly is
(a) A               (b) B              (c) C              (d) D
explain in details 

Dear Student,
The student who is most likely to have done the experiment properly is Student C.
As we know that in case of refraction through a glass slab the incidence ray and emergent ray are lie parallel to each other and make equal angles i.e. angle of incidence = angle of emergence.
So from all the observations done by students A, B, C and D, C has the most accurate readings. So option c is correct.
Regards