Cold Packs, Whose Temperatures Are Lowered When Ammonium Nitrate Dissolves $\Delta$

Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction?

A) . $\Delta$ H < 0, process is exothermic
B) . $\Delta$ H > 0, process is exothermic
C) . $\Delta$ H < 0, process is endothermic
D) . $\Delta$ H > 0, process is endothermic
E) . $\Delta$ H = 0, since cold packs are sealed