The correct answer is 1920. Explanation & Key Takeaways: • The Non-cooperation Movement started in 1920. • The leader of the Non-cooperation Movement was Mahatma Gandhi. • The non-cooperation movement was a mass movement that involved participation from the nationalists as well as the public. • The movement was to be nonviolent and to consist of Indians resigning their titles, boycotting government educational institutions, government service, foreign goods, and elections, and eventually, refusing to pay taxes. • The non-cooperation movement was a mass movement that was launched by Gandhi in 1920. It was a peaceful and non-violent protest against the British government in India. • People had to resign from their government jobs. People were asked to withdraw their children from government-controlled or aided schools and colleges. • After a series of events including the Jallianwala Bagh Massacre, Gandhiji realized that there was no prospect of getting any fair treatment at the hands of the British, so he planned to withdraw the nation's cooperation from the British Government, thus launching the Non-Cooperation Movement and thereby marring the administrative set up of the country. • This movement was a great success as it got massive encouragement from millions of Indians. This movement almost shook the British authorities. Related Concepts: • The Non-cooperation Movement was called off by Mahatma Gandhi after the Chauri Chaura incident in February 1922. • Lord Reading was the viceroy of India when the Chauri Chaura incident took place. • Chittaranjan Das was the President of the Gaya Session of the Indian National Congress held in 1922.