Answer:
examining the answers the correct one is B.
Step-by-step explanation:
In calorimeter there are two possibilities when adding energy to the system,
* energizes it is used to increase the temperature of the particles,
* energy is used to change state, in the latter case there is no increase in temperature, so the curve is flat
Therefore, in a temperature vs. energy curve, the flat parts correspond to changes in the phase, either by raising or lowering the temperature.
when examining the answers the correct one is B