Explanation:

Article 15 (4) enable the state to bring the backward class within the protection of article but not the backward area.

Article 15 of the Indian Constitution prohibits discrimination of Indians on basis of religion, race, caste, sex or place of birth.
Special Provision for the advancement of Backward class: Article 15(4)

• Coming onto the next clause, i.e. Clause (4) of Article 15 of the Indian constitution. It allows the state to enact laws and provisions relating to the advancement of socially and educationally backward classes and the scheduled castes and scheduled tribes.

Socially and educationally backward classes

• The phrase “socially and educationally backward classes” under Article 15(4) refers to underprivileged classes of people who have faced discrimination and prejudice from the privileged class. This category includes the class of people who belong to backward classes in society but are not covered under SCs or STs. OBCs have been included under this phrase of socially and educationally backward classes as a category for reservation.

Hence option 3rd is correct.