Which process is used for the purification of impure metals such as oxide of metals?

Which of the following metals cannot be easily cut by a knife?

A. aluminium

B. sodium

C. potassium

D. lithium

. . . . . . . . is the most ductile metal.

A. Cu

B. Al

C. Au

D. Zn

The chemical structure of the pearl is

A. Calcium Carbonate

B. Calcium Carbonate & Magnesium Carbonate

C. Calcium Chloride

D. Calcium Sulphate

Stainless steel does not rust because

A. chromium and nickel combine with iron

B. chromium forms an oxide layer and protects iron from rusting

C. nickel present in it, does not rust

D. iron forms a hard chemical compound with chromium present in it