Which of the following substances are structural isomers of each other?

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

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

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

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

B