According to which Article of the Indian Constitution, it is obligatory for government to promote welfare of the Other Backward Classes (OBC)?

Correct option is B

Article 340 of the Indian Constitution mandates the government to promote the welfare of the Other Backward Classes (OBC). It authorizes the President to appoint a commission to investigate the conditions of socially and educationally backward classes within the territory of India and recommend steps to improve their condition. Therefore, the correct answer is: (b) Article 340.