A. calcium tetraoxosulphate (IV)
B. calcium hydrogentrionocarbonate (IV)
C. calcium hydroxide
D. calcium trioxocarbonate (IV)
Option D – calcium trioxocarbonate (IV)
Calcium hydrogen carbonate, often present in temporary hard water, is boiled in a kettle to remove the hardness. In the process, a scale forms on the inside of the kettle in a process known as furring of kettles. This scale is composed of calcium carbonate.