Molar volume of a gas is that 1 mol of an ideal gas occupies 22.4 L at standard temperature and pressure.
We have to assume that O₂ behaves similar to an ideal gas.
Volume changes with pressure and temperature, since the question does not specify the temperature and pressure conditions we are assuming its at standard temperature and pressure conditions
volume occupied by 1 mol - 22.4 L
therefore volume occupied by 4.27 mol - 22.4 L/mol x 4.27 mol = 95.65 L
volume occupied by 4.27 mol of O₂ is 95.7 L