Which of the following is a way to decrease the pressure of a gas?increase the volumeincrease the number of moleculesdecrease the volume

To decrease the pressure of a gas, you can increase the volume. This is based on Boyle's law which states that the pressure and volume of a gas have an inverse relationship when temperature is held constant. So, when you increase the volume, the pressure decreases.

Increasing the number of molecules would actually increase the pressure, not decrease it. This is based on the ideal gas law which states that the pressure is directly proportional to the number of molecules (or moles) of gas.

Decreasing the volume would also increase the pressure, not decrease it, again based on Boyle's law.

So, the correct answer is: increase the volume.