Final answer:
The moist adiabatic rate is lower than the dry adiabatic rate because condensation of water vapor in moist air releases latent heat, which makes the temperature decrease more slowly with altitude.
Step-by-step explanation:
The moist adiabatic rate is lower than the dry adiabatic rate because the presence of water vapor in the air requires additional energy to change its state during condensation. This process releases latent heat, which reduces the rate at which temperature decreases with altitude in a rising parcel of moist air, compared to a dry air parcel which cools at a faster rate because it does not release latent heat.