Explanation:

- The Oudh Kisan Sabha was formed to address the grievances of peasants in the Oudh (Awadh) region of Uttar Pradesh.

- Option 1: 1918 — Not the correct year of its formation.

- Option 2: 1920 — This is the correct year. The Sabha was set up by leaders like Jawaharlal Nehru and Baba Ramchandra to organize and empower the peasants.

- Option 3: 1921 — The Sabha was already active by 1921; not the year of its founding.

- Option 4: 1924 — Too late for the formation; it was already functioning well before this.

- The Oudh Kisan Sabha played a crucial role in the peasant movement during the Non-Cooperation Movement.