Which represents an empirical formula?

A.     \({{\text{C}}_{\text{2}}}{{\text{H}}_{\text{4}}}\)

B.     \({{\text{B}}_{\text{2}}}{{\text{H}}_{\text{6}}}\)

C.     \({\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}\)

D.     \({{\text{C}}_{\text{6}}}{{\text{H}}_{\text{6}}}\)

C