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.

Example Input: Question: The outer surface of the heart changes from positive to negative during what? Answer: depolarization
Example Output: The outer surface of the heart changes from positive to negative during depolarization.

Example Input: Question: What happens to most of the energy in a trophic level as it passes to the next higher level? Answer: it is lost
Example Output: As it passes to the next level, most of the energy in a trophic level it is lost.

Example Input: Question: What protects tissues of the central nervous system from changes in ph? Answer: bicarbonate ions
Example Output:
Bicarbonate ions protects tissues of the central nervous system from changes in ph.