Final answer:
A gas will deviate from ideal gas behavior at low temperatures and very high pressures option (a), due to increased intermolecular attractions and a decrease in space between particles.
Step-by-step explanation:
Under what circumstances would you expect a gas to behave significantly differently than predicted by the ideal gas law? You would expect significant deviations from the ideal gas behavior at low temperatures and very high pressures.
At high pressures, the molecules of a real gas are forced closer together, making the volume occupied by the gas particles non-negligible. Meanwhile, at low temperatures, the kinetic energy of the particles decreases, resulting in more prominent attractive forces between the particles.
Therefore, a real gas behaves least like an ideal gas under conditions of high pressure and low temperature.