Which one of the following usages was a post-Vedic development?

Q. Which one of the following usages was a post-Vedic development?

(a) Dharma — Artha — Kama — Moksha

(b) Brahmana—Kshatriya—Vaishya—Shudra

(c) Brahmacharya—Grihastashrama— Vanaprastha — Sanyasa

(d) Indra — Surya — Rudra — Marut

Ans: (c) Brahmacharya—Grihastashrama— Vanaprastha — Sanyasa