We see in the graph how the substance behaves when the temperature is raised. We will assume that the pressure exerted on the substance is constant and that there is no input or output of material. In addition, we will assume that initially, the substance is in the solid phase.
When we apply energy to a substance, it will begin to raise its temperature until it reaches a phase change. This phase change can be solid to liquid or liquid to gas. When there is a phase change the energy that is added is used to make this transition and there will be no increase in temperature.
Now let's see the graph. At points BC and DE the temperature does not change with time, so at these two segments, there is a phase change. BC will be a phase change from solid to liquid and DE the phase change from liquid to gas. Let's see it on the graph
Therefore, the gas phase will be in segment EF
Answer: EF