The air pressure in the rigid tank Decreases.
Step-by-step explanation:
A rigid tank is said to be a region where volume is always considered as a constant. During the process of cooling the rigid tank where the temperature is said to be decreased, the effect of air pressure in the tank also decreases.
Because, PV = RT, where P is the pressure, T is temperature, R is constant, V is the volume. Hence pressure is directly proportional to temperature.