Which of the following is an alloy?

Generally,in what forms are the elements present in the lithosphere?

$A, B$ and $C$ are three elements which undergo chemical reactions according to the following equations:
$A_{2}O_{3} + 2B \rightarrow B_{2}O_{3} + 2A$
$3CSO_{4} + 2B \rightarrow B_{2}(SO_{4})_{3} + 3C$
$3CO + 2A \rightarrow A_{2}O_{3} + 3C$
$(a)$ Which element is the most reactive?
$(b)$ Which element is the least reactive?
$(c)$ What is the type of reactions listed above?

Give reasons for the following:
$(i)$ Most metals conduct electricity well.
$(ii)$ The reaction of iron $(III)$ oxide,$Fe_{2}O_{3}$,with heated aluminium is used to join cracked machine parts.
$(iii)$ Sodium,potassium,and lithium are stored under oil.

What is the color of a potassium dichromate solution?

What is the chemical formula of rust?