Which of the following describes a boiling point?
A. Phase change from a solid to a liquid occurring at a specific
temperature and pressure
B. Phase change from a liquid to a gas occurring at a specific
temperature and pressure
c. Phase change from a gas to a liquid occurring at a specific
temperature and pressure
D. Phase change from a solid to a gas occurring at a specific
temperature and pressure

Phase change from a liquid to a gas occurring at a specific  temperature and pressure

Explanation:

Boiling is a physical process in which a substance changes its state from liquid to vapor state.

In this context ,boiling point is the threshold temperature at which changes of state from liquid to vapor occurs. The boiling point also depends upon atmospheric pressure of environment as well. For the same substance, boiling point at  two different pressure will differ significantly.

For example : Boiling point of water at sea level is 100 degree Celsius

while at 6,250 ft , Boiling point of water  is 93.4 degree Celsius.

Based on above discussion option B Phase change from a liquid to a gas occurring at a specific  temperature and pressure is the correct answer.

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.