Q. Enthalpy of a substance is defined as

• (A) The sum of internal energy and the work done in forcing unit mass of substance into an enclosure at the constant pressure at which the substance exists
• (B) Sum of sensible heat + latent heat of substance
• (C) Total heat content of substance above zero degree centigrade
• (D) Sensible heat of water + work done in forcing unit mass of substance into an enclosure at constant pressure at which the substance exists