Right choice is (d) It is the temperature at which an ideal gas will have zero pressure, assuming it stays a gas
Easiest explanation: Absolute zero has been defined as the temperature at which an ideal gas would have zero pressure, assuming it remains a gas till then. The temperature value is obtained by extrapolating the graph of Pressure vs Temperature till the straight line cuts the temperature axis. This gives us a value of -273.15°C. Note that this temperature hasn’t been achieved yet.
