Which compound is not an isomer of hexane?

A.     ${\text{C}}{{\text{H}}_{\text{3}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{\text{)C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}$

B.     ${\text{C}}{{\text{H}}_{\text{3}}}{\text{CHCHC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}$

C.     ${{\text{(C}}{{\text{H}}_{\text{3}}}{\text{)}}_{\text{3}}}{\text{CC}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}$

D.     ${\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{CH(C}}{{\text{H}}_{\text{3}}}{\text{)C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{H}}_{\text{3}}}$

B