60. The PV curve for the van der Waals equation at a fixed temperature is plotted in Fig. 13. In this case, the liquid phase can coexist with the gas phase at pressure Pc. The pressure Pc intercepts with the PV curve at three points: a, c, and e, respectively. And the slope of the PV curve vanishes at b and d. Which of the following statements is correct? (A) For pressure a bit higher than PC, it is impossible to have a stable gas phase. (B) For pressure a bit lower than PC, the gas phase is more stable than the liquid phase. (C) The region a→ b is the supercooled liquid region. (D) The region b → c → d corresponds to a fluid with a positive compressibility. (E) None of the above.