A student has to perform an experiment on tracing the path of a ray of light passing through a rectangular glass slab for three different angles of incidence. Two of his friends suggest the following options to him: (A) Draw the incident rays corresponding to 20o, 50o and 70o as angles of incidence and fix the two pins on the incident ray just 2 cm apart. (B) Draw the incident rays corresponding to 30o, 45o and 60o as the angles of incidence and fix two pins on the incident rays nearly 8 cm apart. Which is the better option he should follow? Give reason in support of your answer.