The enthalpy of a system is the same as its:
a. specific heat.
b. heat of reaction.
c. heat of combustion.
d. heat content.

The answer for above statement:

D. heat content.

Explanation:

Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.

Heat content - (thermodynamics) a physical science amount adequate the interior energy of a system and the merchandise of its volume and pressure.

that's what i got you can count the number of atoms