Why was the role of different groups necessary in making Non-Cooperation a mass movement?

Correct answer: The movement became broad when students, lawyers, traders, peasants, and other groups joined

A mass movement is governed by broad participation rather than the action of one leader or one class. During Non-Cooperation, students, lawyers, traders, peasants, workers, and other groups joined through different forms of boycott and protest. Their participation expanded the movement’s social reach and pressure on colonial rule. Thus A is correct; B, C, and D contradict the meaning of mass mobilisation.