Answer: The correct answer is pressure and volume.
Step-by-step explanation:
Boyle's law is one of the law used to determine the combine gas law.
This law states that the pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.
Mathematically,
(At constant temperature and number of moles)
or,

where, k is the proportionality constant
P = Pressure of the gas
V = Volume of the gas
Hence, the correct answer is pressure and volume.