Sketch shows the plot of Z v/s P for a hypothetical gas for one mole at three distint temperature. Boyle's temperature is the temperature at which gas shows ideal behaviour over a pressure range in the low pressure region.Boyle's temperature (T_b)=a/(Rb).If a plot is obtained at temperature well below Boyle's temperature then the curve will show negative deviation, in low pressure region and positive deviation in the high pressure region. Near critical temperature the curve is more likely as CO_2 and the temperature well above critical temperature curve is more like H_2 at 0^@C as shown above.At high pressure suppose all the constant temperature curve varies linearly with pressure according to the following equation : Z=1+(Pb)/(RT) (R=2 cal "mol"^(-1) K^(-1)) In very high pressure region if Z v/s P is plotted at 1200 K for the above gas then it will have greatest slope.