CThe temperature must be less than the critical temperature
c
The following graph below illustrates a $(T-b)$ diagram of a matter.
The line $l$ corresponds to a liquid line saturated. The line $g$ corresponds to a saturated gas line:
The vegion between is the wet region (both lignid and gas). $T_{c}$ corresponds to the critical temperature.
So, it is clear that the temp must be below the critical temperature for a matler to exist simultaneously as gas and liquid.
Correct choice - option-$C$
