Under Article 355 of the Constitution of India, it is the duty of the Union to ? [UPSC CAPF 2015]
(a) protect States against external aggression and internal disturbance
(b) allow the extension of executive powers of the Union to any State
(c) declare that the powers of the Legislature of a .State shall be exercisable by or under’ the authority of the Parliament
(d) allow the Parliament to include or exclude any caste, race or tribe into the list of the Scheduled Castes or Scheduled Tribes