Hypothetical elements A₂ and B₂ react according to the following equation, forming the compound AB.

A₂(aq) + B₂(aq) → 2AB(aq); ∆H° = +271 kJ/mol

If solutions A₂(aq) and B₂(aq), starting at the same temperature, are mixed in a coffee-cup calorimeter, the reaction that occurs is

a. Exothermic, and the temperature of the resulting solution rises.

b. Endothermic, and the temperature of the resulting solution rises.

c. Endothermic, and the temperature of the resulting solution falls.

d. Exothermic, and the temperature of the resulting solution falls.

e. Exothermic or endothermic, depending on the original and final temperatures.