Which of the following processes described below is irreversible?

The increase in temperature of an iron rod by hammering it

A gas in a small container at a temperature $T_1$ is brought in contact with a big reservoir at a higher temperature $T_2$which increases the temperature of the gas

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

All of the above