while tracing the path of a ray of light passing through a rectangular glass slab a student tabulated his observations as given below: S.N.O ∠i ∠r ∠e I 60⁰ 39⁰ 61⁰ II 50⁰ 36⁰ 51⁰ III 40⁰ 28⁰ 39⁰ IV 30⁰ 20⁰ 31⁰ The correct observation is: A) I B) II C) III D) IV