A gas is said to behave like an ideal gas when the relation PV / T = constant. When do you expect a real gas to behave like an ideal gas?
When the temperature is low
When both the temperature and pressure are low
When both the temperature and pressure are high
When the temperature is high and pressure is low
At high temperature and low pressure, the value of Z approaches unity.
Therefore,
is the ideal gas equation and it is followed by the real gas when the temperature is high and pressure is low.
Hence, Option (4) is correct