18. For the reaction A + B → C + D, ∆H° = +40 kJ and AS° = +50 J/K. Therefore, the reaction under standard conditions is (A) spontaneous at temperatures less than 10 K.; (B) spontaneous at temperatures greater than 800 K.; (C) spontaneous only at temperatures between 10 K and 800 K.; (D) spontaneous at all temperatures ; (E) nonspontaneous at all temperatures.