Why did Gandhi consider non-cooperation an effective weapon against colonial rule?

Correct answer: Because colonial rule depended on Indian cooperation

Gandhi’s governing idea was that colonial rule did not rest only on British force; it also depended on Indian participation in administration, schools, courts, markets and other institutions. If people peacefully withdrew that cooperation, the machinery and moral authority of colonial rule would weaken. Therefore Non-Cooperation was a mass, non-violent strategy. The other options are either factually false or irrelevant.