H₂ and F₂ React According to the Following Equation,forming HF

H₂ and F₂ react according to the following equation,forming HF.
H₂(g) + F₂(g) → 2HF(g) ; ΔH° = -271 kJ
If H₂(g) and F₂(g) were mixed in a thermally insulated vessel,the reaction that occurred would be

A) endothermic,and the temperature of the reaction system would fall.
B) We could not tell unless the original and final temperatures were given.
C) exothermic,and the temperature of the reaction system would fall.
D) exothermic,and the temperature of the reaction system would rise.
E) endothermic,and the temperature of the reaction system would rise.