Which of the following is an alloy?

Give reasons for the following:
$(i)$ Carbon can reduce zinc oxide to zinc but not calcium oxide to calcium.
$(ii)$ Copper and aluminium wires are usually used for electricity transmission.

What are the constituent elements of Magnalium?

$2 \, mL$ each of concentrated $HCl$,$HNO_3$,and a mixture of concentrated $HCl$ and concentrated $HNO_3$ in the ratio of $3:1$ were taken in test tubes labeled as $A$,$B$,and $C$. $A$ small piece of metal was put in each test tube. No change occurred in test tubes $A$ and $B$,but the metal dissolved in test tube $C$. The metal could be:

$(i)$ Name a metal which does not stick to glass.
$(ii)$ Name the metal which is commonly used in thermite welding.
$(iii)$ What is the nature of zinc oxide?

An alloy is