Final answer:
Gases most likely to deviate from ideal behavior at high pressure and low temperature, where their volume and intermolecular attractions become significant. The correct option is b) High pressure, low temperature.
Step-by-step explanation:
Gases are most likely to deviate from ideality under the set of conditions where both pressure and temperature affect the behavior significantly. At high pressure and low temperature, gases deviate most from the ideal gas behavior. High pressure reduces the distance between gas molecules, making their own volume more significant relative to the space they occupy.
Low temperature decreases the kinetic energy of the gas molecules, leading to an increase in intermolecular forces. These factors lead to a deviation from the assumptions made in the ideal gas law. So, the correct option is b) High pressure, low temperature.