When does gas deviate the most from its ideal behavior?
(A) at low pressure and high temperature
(B) at high pressure and high temperature
(C) at low pressure and low temperature
(D) at high pressure and low temperature

Hint: According to the kinetic theory of gases states that ignore both all the interactions between molecules are attractive or repulsive and the volume occupied by the molecules of a gas, but all real gases are non-zero volumes. These real gases' molecular interaction depends on the structure of molecules and changes with a gaseous substance.

Complete step by step solution:
The real gases do not obey the ideal gas laws and do not behave as predicted in the kinetic molecular theory of gas. Hence, real gas does not behave as ideal gases in such conditions.
At higher temperatures and low pressure, all real gases act as ideal gases. Because in such conditions mentioned the gas molecule occupied volume is negligible and those interactions between the molecules also negligible.
The molecules of real gas have a small volume and the gaseous molecules of real gas are relatively far apart at low pressure. If the pressure increases in real gas the intermolecular distance becomes smaller than before.
At high pressure and low temperature, the molecules of real gas close each other with significant volume and intermolecular forces should not be neglected.

Hence, the correct answer is option D.

Note: At high temperatures, the molecules of real gas have sufficient kinetic energy to overcome intermolecular attractive forces. To overcome the modified ideal gas for describing the behavior of real gas by including the effects of molecular forces and molecular size by the Van Der Waals equation.