Explanation:

Both (a) and (b) are correct

The two most contentious issues in the application of Article 15(4) as well as Article 16(4) have been:

• (i) Determination of backward classes.

Backward classes is not defined in the constitution. Article 340 however empowers the president to appoint a commisision to investigate conditions of socially and educationally backward classes. On the basis of the report of the commission, the president may specify as to who are to be considered as backward classes. In Balaji v State of Mysore, the Mysore Govt issued an order under Article 15(4) reserving seats in the medical and engineering colleges of the state as follows- backward Classes 28%, more Backward Classes 20%, Sc And ST 18%. Thus 68% of the seats were reserved and only 32% were made available in the merit pool.The court held that the sub classification made by the order between backward classes and more backward classes was not justified under article 15(4). Backwardness as envisaged by the article must be both social and educational and not either social or educational. Caste cannot be the sole test for ascertaining backwardness. Poverty , occupation, place of habitation are relevant factors and need to be taken into consideration. The impugned order, however proceeds only on the basis only on the basis of caste without regard to other factors and that is sufficient to render the invalid.

• In Jayasree v. State of Kerala, the supreme court held that neither caste by itself nor poverty by itself is a determining factor of social backwardness.
• P Rajendran v State of Madras- SC upheld the test of backwardness which was solely based on caste and was contravening to Balaji Judgement.
• KC Vasanth Kumar v State of Karnatka – Both caste and poverty would be relevant factors in determining backwardness and caste cannot be the sole criteria as the term used in Article 15 is class and not caste. Both social and educational backwardness should be kept in ind before formulating a reservation policy.

Hence option 3rd is correct.