Final answer:
Latent heat is the correct answer from the provided options and it pertains to the energy required for phase changes in a substance without a temperature change, typically measured in J/kg or Btu/pound.
Step-by-step explanation:
Among the provided options, the quantity that is expressed in British Thermal Units (BTU) per pound of dry air is the latent heat. Latent heat refers to the amount of energy in the form of heat that is required for a substance to undergo a phase change without a change in temperature. This concept involves two main types of latent heat: the heat of fusion (Lf), which is the energy required for a substance to transition between solid and liquid phases, and the heat of vaporization (Ly), which is the energy required for a substance to transition between liquid and gaseous phases. Both Lf and Ly are known as latent heat coefficients and are typically measured in units of J/kg. However, when it comes to air conditioning and heating applications, especially in the United States, latent heat can also be discussed in Btu per pound of dry air.