What do the horizontal portions of the graph represent? When heat is added to or removed from the substance and the temperature remains the same, where is the thermal energy going? Why?

Harry lives in a city, and he has a lung condition known as asthma. on certain days, harry has to stay inside because pollutants in the air make it difficult for him to breathe. which of these pollution sources are nonpoint sources that might bother harry if he goes outside? choose the two that apply.