It is very important to open oil drain valves and plugs in the crankcase for which of the following reasons?
a) The oil is very hot.
b) The oil is very cold.
c) Residual pressure in the crankcase may blow refrigerant vapour and oil out.
d) Old oil is contaminated with refrigerant and may be very acidic.
e) Oil can never be drained below the critical minimum level.
Answer: C