Match the following and choose the correct option.

(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

The correct answer is option 3. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i).

Here's the explanation for each match:

(a) Bleaching powder (CaOCl₂): Used as a disinfectant and bleaching agent, not for setting bones (iv).

(b) Baking soda (NaHCO₃): Commonly used as an antacid to neutralize stomach acid (iii).

(c) Washing soda (Na₂CO₃): Effective in removing water hardness (ii).

(d) Plaster of Paris (CaSO₄·½H₂O): Primarily used for making casts and molds, including those supporting broken bones (i).

Therefore, option 3 correctly matches the compounds with their respective uses.