31. Which of the following statements about thermodynamic processes involving an ideal gas are correct? (A) In an isothermal process, ΔE = 0, and PV is a constant. (B) In an adiabatic process, q = 0, and PV is a constant. (C) In free expansion into a vacuum, the gas does no work. (D) The maximum work from an isothermal expansion is obtained only when the process is carried out reversibly through infinitesimal changes. (E) In a cyclic process, all state functions return to their initial values, and the overall work and heat are always zero.