Final answer:
The boiling point of a liquid is when its vapor pressure matches the external atmospheric pressure; the flash point is when vapor pressure meets the liquid's lower flammability limit. The correct answer is a) Boiling, flash
Step-by-step explanation:
The boiling point of a liquid occurs when the vapor pressure of the liquid equals the external atmospheric pressure. This is the temperature at which the liquid starts to boil, forming bubbles of vapor throughout the liquid. On the other hand, the flash point of a liquid occurs when the vapor pressure of the liquid equals its lower flammability limit. This is the temperature at which the liquid's vapors can ignite when exposed to a flame or spark.