The enthalpy of combustion of cyclohexane, cyclohexene and $H_2$ are respectively -3920, -3800 and -241 kJ/mol. The heat of hydrogenation of cyclohexane is

Question

(a) -121 kJ/mol
(b) +121 kJ/mol
(c) -242 kJ/mol
(d) +242 kJ/mol