Answer: the best option to answer the question is letter A ("sloped")
Explanation:
The question requires us to identify how a temperature change is represented in heating and melting curves.
A heating curve represents the relationship between the temperature, states of matter of a substanceand heat added to this substance.
The changes of state of the substance are represented by flat lines, where the temperature remains constant, indicating that the value in the y axis (temperature) does not change while the value in the x axis is changing .
The temperature change, on the other hand, is represented by sloped curves, indicating that the value in the y axis (temperature) is changing as the value in the x axis (heat added) also changes).
Therefore, the best option to answer the question is letter A ("sloped").
