The correct option is C The principle of separate electorate was rejected in Lucknow Pact.
Explanation:
After the split, the Congress came to be dominated by the Moderates with Tilak’s followers functioning from outside. The two groups reunited in 1916 with the signing of Lucknow Pact.
Option (a), (b) and (d) are correct: The Lucknow Pact in 1916 offered a joint League-Congress scheme for constitutional reforms, demanding representative government and dominion status for India and proportional representation in both imperial and provincial legislature was agreed upon. In 1917 the Muslim League supported the Home Rule agitation started by Annie Besant. The outbreak of communal riots in Bihar, United Provinces and Bengal soon after this rapprochement revealed the continuing disjunction between the masses and their leaders. The latter's lingering faith in constitutional politics suffered a further jolt when the Montagu-Chelmsford Reforms in 1919 disregarded the Lucknow Pact.
Option (c) is incorrect: The principle of separate electorate was accepted.