The relative molecular mass of a gas is 56 and its empirical formula is ${\text{C}}{{\text{H}}_{\text{2}}}$. What is the molecular formula of the gas?

A.     ${\text{C}}{{\text{H}}_{\text{2}}}$

B.     ${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{4}}}$

C.     ${{\text{C}}_{\text{3}}}{{\text{H}}_{\text{6}}}$

D.     ${{\text{C}}_{\text{4}}}{{\text{H}}_{\text{8}}}$

D