The correct option is
B Cannot be determined
Mohini is mother-in-law of Sunita and grandmother of Nanu. Vinod is grandfather of Tanmay. So, Nanu and Tanmay represent third generation.
Mohini and Vinod form a couple and represent first generation.
Clearly, Roha and Sunita form the other couple and represent second generation.\
Rohan is a CA. Since engineer is married, so Vinod is an engineer and likes red colour.
Mohini is a teacher and likes orange colour.
Nanu likes blue colour.
Tanmay is a Principal and likes black colour.
Sunita, Nanus mother, likes white colour.
Clearly, Rohan likes green colour.
The only clue that Sunita, Rohan's wife, is not a doctor, cannot lead to her correct profession. So, the data is inadequate.