Which of the following represents an endothermic reaction?

Select one:

a. S(s) +O2(g) → SO2(g) ΔH = -297kJ

b. 2NO2(g) → N2(g) + 2O2(g) + 33.8kJ

c. N2(g) + 2O2(g) + 90.4kJ → 2NO2

d. N2H4(g) + O2(g) → N2(g) +2H20(g) + 627.6 kJ