Exp) Option a is the correct answer.

Mahatma Gandhi had always opposed untouchability and advocated for the upliftment of the Depressed Classes, whom he later referred to as Harijans (meaning “Children of God”). However, it was after the Poona Pact of 1932 that the upliftment of Harijans became a central focus of his social and political programme.

Following this event, Gandhi intensified his efforts to abolish untouchability. He started a nationwide campaign for Harijan welfare, including setting up the Harijan Sevak Sangh, writing in Harijan journals, and engaging in public efforts to open temples and wells to the so-called untouchables.

Source: Unit-10.pdf