A real gas deviates most from ideal behaviour

We know that in ideal behavior we can consider that gases do not attract each other, i.e. there are no intermolecular forces of attraction.

While at high pressure and low temperature, gaseous atoms or molecules get closer to each other and van der Waal forces operate. So, molecules or atoms start attracting each other. Hence a gas deviates the most from its ideal behavior.

Therefore, option (B) is the answer.