(i) impurities of low boiling metals can be separated by distillation.

(ii) impurities are more soluble in molten metal than in solid metal.

(iii) different components of a mixture are differently adsorbed on an absorbent.

(iv) vapours of the volatile compound can be decomposed in pure metal.

Correct Answer: (ii) impurities are more soluble in molten metal than in solid metal

Explanation:  The Zone refining is based on the principle that the impurities are more soluble in molten metal than in solid metal.