The correct answer is (C) a-iii, b-iv, c-ii, d-i
Sardar Sarovar – Narmada; Salal – Chenab; Gandhi Sagar – Chambal; Hirakud – Mahanadi.
The passage explicitly states Sardar Sarovar is on the Narmada and Hirakud is in the Mahanadi basin. Salal Dam is on the Chenab (Jammu & Kashmir) and Gandhi Sagar is on the Chambal — standard NCERT facts from Chapter 3. Students should memorise dam–river pairs as they appear frequently in MCQs and map-based questions.