Solution:The last session of Indian National Congress attended by Bal Gangadhar Tilak was the Amritsar Session, 1919.He had mellowed sufficiently to oppose Gandhi's policy of boycotting elections to legislative councils established as part of the reforms from the Montagu-Chelmsford Report to Parliament in 1918. Instead, Tilak advised delegates to follow his policy of "responsive cooperation" in carrying out reforms. He passed away on 1st August, 1920.