The air loss rate for a straight truck or bus with the engine off and the brakes
applied should not be more than:
(a) 1 psi in 60 seconds
(b) 1 psi in one minute
(c) 2 psi in 45 seconds
(d) 3 psi in one minute

D

Explanation:

The air loss rate for a straight truck or bus with the engine off and the brakes applied should not be more than (D) 3 psi in one minute. An air loss rate  greater than 3 psi per minute can cause damage to air tank so the to avoid such condition the air leak rate cannot be more than 3 psi per minute.

oil flow is a highly convective flow compared to water flow at normal temperature and pressure.