In lower temperatures, the molecules of real gases tend to slow down enough that the attractive forces between the individual molecules are no longer negligible. In high pressures, the molecules are forced closer together- as opposed to the further distances between molecules at lower pressures. This closer the distance between the gas molecules, the more likely that attractive forces will develop between the molecules. As such, the ideal gas behavior occurs best in high temperatures and low pressures. (Answer to your question: C)  This is because  the attraction between molecules are assumed to be negligible in ideal gases, no interactions and transfer of energy between the molecules occur, and as temperature decreases and pressure increases, the more the gas will act like an real gas.
