Which of the process described below are irreversible?

Options

A. The increase in temperature of an iron rod by hammering it.
B. A gas in a small contianer at a temprture `T_1` is brought in contact with a big reservoir at a higher temperature `T_2` which increases the temperature of the gas.
C. A quasi-static isothermal expansion of an ideal gas in cylinder fitted with a frictionless piston.
D. an ideal gas is enclosed in a piston cylinder arrangement with adiabatic walls. A weight W is added to the piston, resulting in compression of gas.