18. Which of the following organisms are
producers?
A. humans
B. bears
C. trees
D. fungi
19.

Trees are producers

I hope this helps

Trees

Explanation:

Trees are the only thing on the list that does nothing but help the environment/produce. Its not fungi because fungi is literal harmful bacteria that molded.

Changing the amount of heat energy usually causes a temperature change. However, during the phase change, the temperature stays the same even though the heat energy changes. This energy is directed into changing the phase and not into raising the temperature. That's why the temperature of water doesn't increase as it is boiling.