1. A substance in gaseous form is being cooled to solid state. Its temperature will remain constant when the substance is

   1. (i) in condensing phase

   2. (ii) in freezing phase

   (iii) at thermal equilibrium with the environment.

A. (i) only B. (iii) only
C. (i) and (ii) only D. (i), (ii) and (iii)