A student boils 100 grams of water to form water vapor (gas). What method should the student use to determine that the mass of the water vapor is equal to 100 grams?

Choose your answer from:
a). measuring the amount of water vapor (gas) in the air
b). collecting the water vapor (gas) and cooling it back to a liquid
c). weighing the beaker before and after the water is boiled
d). comparing the temperature of the boiling water to the temperature of the water vapor (gas)
b).