According to the ideal gas law \( PV = nRT \), if the volume \( V \) is held constant and the temperature \( T \) increases, the pressure \( P \) would increase. This is because, with a constant number of moles of gas \( n \) and the ideal gas constant \( R \), an increase in temperature results in a proportional increase in pressure.
Therefore, the correct response is:
It would increase.