Solution:(b) Brinda said to her doctor, " I am leaving for Boston tomorrow." (Correct)(a) Brinda told her doctor, I was leaving for Boston tomorrow." (Change of reported speech to past continuous is incorrect.)
(c) Brinda had told her doctor, "She was leaving for Boston the next day."(Reported verb and reported speech are incorrect)
(d) Brinda told to her doctor, "I will be leaving for Boston the next day."(Change of reported speech to future continuous and also reported verb is incorrect)