The correct option is B latent heat of fusion
A quantity of heat required to change the unit mass of a solid substance, from solid state to liquid state, while the temperature remains constant, is known as latent heat of fusion.
A quantity of heat released to change the unit mass of a liquid substance, from liquid state to solid state, while the temperature remains constant, is known as latent heat of condensation.
A quantity of heat required to change the unit mass of a liquid substance, from liquid state to vapour state, while the temperature remains constant, is known as latent heat of vapourisation.
A quantity of heat required to change the unit mass of a solid substance, directly from solid state to vapor state, while the temperature remains constant, is known as latent heat of sublimation.