Answer: 2. volume
Step-by-step explanation:
Pressure of the gas is defined as the force exerted by the particles on the walls of the container. It is expressed in various terms like 'mmHg', 'atm', 'kiloPascals' etc.
Volume of the gas is defined as the space occupied by a substance. It is expressed in units like
,
, L and ml.
Mass is the amount of matter contained in a substance. It can be measured in units of kilograms (kg), grams (g), milli grams (mg) etc;
Horsepower is a unit of measurement of power or the rate at which work is done.
Thus volume describes the number of liters of gas trapped in a bottle.