Which non-metal element possesses luster?

Explain the following:
$(a)$ $NaCl$ is not a conductor of electricity in solid state,whereas it does conduct electricity in aqueous solution as well as in molten state.
$(b)$ Iron articles are galvanised.
$(c)$ Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.

What are the substances added to a catalyst to increase its efficiency called?

Which gas is responsible for acid rain?

Which metal oxide cannot be reduced by carbon?

What is the chemical formula of rust?