What is number 3 on the animal cell

Would really appreciate it, i have an idea but not completely sure

The greenhouse effect a. something that has occurred for millions of years b. an unnatural phenomenon caused by humans that maintains earths temperature range. c. the results of the differences in the angle of the suns rays d. an unnatural phenomenon that causes heat energy to be radiated back into the atmosphere

This is the interaction of two organisms where one is and the other is neither nor harmed.