Which of the following property is generally not shown by metals? 

Options

A. Electrical conduction
B. Sonorous in nature
C. Dullness
D. Ductility

Answer

C

Explanation

A metal has a shining surface only when it is fresh. The metals lose their shine or brightness on keeping in air for a long time and acquire a dull appearance due to the formation of a thin layer of oxide, carbonate or sulphide on their surface.
 If we rub the dull surface with a sand paper, the metal objects becomes shiny and bright once again.