Helium behaves most like an ideal gas under which of the following conditions?

Helium behaves most like an ideal gas under conditions of low pressure and high temperature due to the nature of gases and the ideal gas law, which describes the behavior of an ideal gas as being independent of intermolecular forces and molecular volume. Under low pressure, the molecules are far apart, reducing the effects of these intermolecular forces, making helium's behavior closer to that predicted by the ideal gas law.

At high temperatures, the kinetic energy of the gas molecules increases, which further allows them to overcome any minor attractive forces that might be present, allowing helium to expand freely without significant interaction among gas particles. This combination maximizes the ideal gas behavior by minimizing the influences of intermolecular forces and maximizing the average molecular speeds.

The other situations, such as high pressure and low temperature, would lead to more significant intermolecular attractions and repulsions, veering from ideal gas behavior. Therefore, it is the low-pressure and high-temperature conditions that provide the best scenario for helium to behave like an ideal gas.