The reason why Gandhiji attended the Second Round Table Conference of December 1931,
b) The signing of the Gandhi Irwin Pact in March 1931.
Gandhiji attended the Second Round Table Conference because he had signed the Gandhi-Irwin Pact, which led to the suspension of the Civil Disobedience Movement and allowed him to participate in the conference as a representative of the Indian National Congress to discuss constitutional reforms for India with the British government; this pact was a compromise reached between Gandhi and the Viceroy, Lord Irwin, to end the movement and engage in dialogue with the British authorities.