Answer :
B. is positive
H20 (l)--> H20 (g)
when that happens, the heat is absorbed into the liquid to change the state of the liquid to gas; therefore, in order to change to a gaseous state, heat must be a reactant. and so enthalpy is increasing
H20 (l)--> H20 (g)
when that happens, the heat is absorbed into the liquid to change the state of the liquid to gas; therefore, in order to change to a gaseous state, heat must be a reactant. and so enthalpy is increasing