Boiler Scale Can Be Formed on the Walls of Hot

Boiler scale can be formed on the walls of hot water pipes from ground water due to

A) transformation of HCO₃^- ions to CO₃^2- ions, which then form precipitates with the "hardness ions", Ca²⁺, Mg²⁺, Fe²⁺/Fe³⁺.
B) transformation of HSO₃^- ions to SO₃^2- ions, which then form precipitates with the "hardness ions", Ca²⁺, Mg²⁺, Fe²⁺/Fe³⁺.
C) transformation of HSO₄^- ions to SO₄^2- ions, which then form precipitates with the "hardness ions", Ca²⁺, Mg²⁺, Fe²⁺/Fe³⁺.
D) transformation of H₂PO₄^- ions to PO₄^3- ions, which then form precipitates with the "hardness ions", Ca²⁺, Mg²⁺, Fe²⁺/Fe³⁺.
E) reaction of the CO₃^2- ions present in all ground water with the "hardness ions", Ca²⁺, Mg²⁺, Fe²⁺/Fe³⁺.