Match the following items in column I with the corresponding items in column II.

• (i) $$\text{Na}_2\text{CO}_3\cdot10\text{H}_2\text{O}$$ (Washing Soda): Manufactured on a large scale using the Solvay process.
  $$\implies \text{(i)} \rightarrow \text{(C)}$$
• (ii) $$\text{Mg(HCO}_3)_2$$ (Magnesium Bicarbonate): Soluble hydrogencarbonates of calcium and magnesium are directly responsible for causing temporary hardness in water.
  $$\implies \text{(ii)} \rightarrow \text{(D)}$$
• (iii) $$\text{NaOH}$$ (Sodium Hydroxide): Industrially prepared by the electrolysis of brine solution in the Castner-Kellner process.
  $$\implies \text{(iii)} \rightarrow \text{(B)}$$
• (iv) $$\text{Ca}_3\text{Al}_2\text{O}_6$$ (Tricalcium Aluminate): An essential component found in Portland cement ingredients that helps regulate its setting time.
  $$\implies \text{(iv)} \rightarrow \text{(A)}$$

Conclusion:

Aligning the correct pairs leads directly to the proper combined option sequence.

Answer: (i) → (C); (ii) → (D); (iii) → (B); (iv) → (A)