In thermochemistry, what is known about a reaction with a positive enthalpy change $\Delta H>0$?

• A. The reaction must be spontaneous at all temperatures ($\Delta G<0$).
• B. The reaction is endothermic and absorbs heat from the surroundings.
• C. The reaction has no heat exchange with the surroundings ($\Delta H=0$).
• D. The reaction is exothermic and releases heat to the surroundings.

Answer: (B)