From the diagram above, an ideal gas is represented by

Correct answer: N

Explanation: For an ideal gas at fixed temperature, Boyle’s law gives PV = constant. On a graph of PV (y-axis) against P (x-axis), a constant value is shown by a horizontal straight line. In the diagram, the horizontal line is labelled N, so it represents ideal-gas behaviour.

• M — Sloping upward: PV increases with pressure → real-gas deviation (not ideal).
• N — Horizontal line: PV is constant → ideal gas.
• K — Not horizontal; PV changes with P → real gas.
• L — Not horizontal; PV changes with P → real gas.