In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

Question: What is the unit of evolution? Answer: population
Population is the unit of evolution.

Question: Most of the energy used by living things comes either directly or indirectly from what? Answer: the sun
Most of the energy used by living things comes either directly or indirectly from the sun.

Question: In an electromagnetic wave, what do the crests and troughs represent? Answer: oscillating fields

In an electromagnetic wave, the crests and troughs represent oscillating fields.