Explanation:

Both (a) and (b)

• The idea of equality is that like should be treated alike and different treatment may be accorded to those who are sharply dissimilar. Thus, right to equality permits classification. One of the facets of equality is equality of opportunity in the matters of public employment, as guaranteed in Article 16(1). In Indra Sawhney the nine-judge bench observed that under Article 16(1), appointments and/or posts can be reserved in favour of a class. Thus, reservation in state services in favour of backward classes may be made under Article 16(1) too, as it is based on the premise of equality. Articles 16(4) and 16(4A), under which the state may make provision for reservation and reservation in promotion respectively, are constitutionally sanctified classifications and illustrations of Article 16(1). In M. Nagaraj, the Constitution bench made it very explicit by saying that, “in our view, equality as a concept is retained even under Article 16(4A).”
• Thus, arbitrary denial of reservation in promotion is a violation of the right to equality under Article 14, which says, “The state shall not deny to any person equality before the law and equal protection of laws…” Therefore, reservation in public employment and reservation in promotion is a fundamental right under Article 14 read with Article 16(1), 16(4) and 16(4A). Thus, (1) a government order arbitrarily denying reservation or reservation in promotion in favour of backward classes, or (2) a notification advertising certain vacancies for public post(s) without reserving posts as per rules in favour of inadequately represented backward classes, are violative of these fundamental rights and thus may be challenged under Articles 32 or 226 of the Constitution.

Hence option 3rd is correct.