Answer:
b. pressure
Step-by-step explanation:
The boiling point of a substance increases as the pressure increases. The boiling points of a liquid is the temperature at which the liquid converts to vapor. At this point the vapor pressure of the liquid is equal to the pressure surrounding the liquid.
Heating increases the temperature of liquid, thereby increasing the pressure . As pressure increases the energy required to boil also increases, causing an increase in the boiling points.