After the Chauri-Chaura incident in 1922, Mahatma Gandhi decided to suspend the Non-Cooperation Movement. This incident occurred in Chauri-Chaura, Uttar Pradesh, where a group of protesters turned violent and set a police station on fire. Gandhiji was deeply saddened by this act of violence and believed that the movement should be suspended as it had lost its non-violent character.

The Non-Cooperation Movement was launched by Gandhi in 1920 to protest against the repressive British colonial rule in India. It aimed to bring about independence through peaceful means, such as boycotting British goods, resigning from government jobs, and boycotting educational institutions. However, after the Chauri-Chaura incident, Gandhi realized that the movement needed to be halted to prevent further violence and ensure that the principle of non-violence was upheld.

Hence, option 3 - Non-Cooperation Movement, is the correct answer.