Fig. shows the variation in temperature with time when some wax cools from the liquid phase to the solid phase. In which part of the curve, the wax is in liquid phase ?

$PQ$.

In part $PQ$, the state is liquid and temperature is decreasing, In part $QS$ there is change of state from liquid to solid, i.e., this stage is freezing, without change in temperature. In part $ST$, state is solid and temperature is decreasing with time.