A steel cylinder at sea level contains air at a high pressure. Attached to the tank are two gauges, one that reads absolute pressure and one that reads gauge pressure. The tank is then brought to the top of a mountain.
Which statement is true for the gauge that reads gauge pressure?

a. Both gauges will change by the same amount.
b. The pressure reading increases.
c. The pressure reading stays the same.
d. The pressure reading decreases.