(i) CO3^2-, NO^3-

(ii) ClO^3- , CO3^2-

(iii) SO3^2-, NO^3-

(iv) ClO^3- , SO3^2–

Correct Answer: (i) CO3^2-, NO^3-

Explanation: CO3^2- and NO^3- are the pairs of ions that are isoelectronic and isostructural.