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: Which is the best explanation for how air masses move across the United States? Answer: The prevailing westerlies move air masses from west to east across the United States but may be deflected by the jet stream.
The best explanation for how air masses move across the united states is that the prevailing westerlies move air masses from west to east across the united states but may be deflected by the jet stream.