In `C_(2)H_(4)` energies of formation of `(C=C) and (C-C)` are -145 kJ/mol and -80kJ/mol respectively. What is the enthalpy change w hen ethylene polymerises to form polythene?
A. `+650kJ//mol`
B. `+65kJ//mol`
C. `-650kJ" "mol^(-1)`
D. `-65kJ" "mol^(-1)`