What source would be most useful in determining the reliability of Punxsutawney Phil's predictions over a number of years?
A. A memoir from a member of The Groundhog Club
B. A historical survey of customs in Pennsylvania
C. A record of weather patterns in the last decade
D. An encyclopedia entry on mammals in the northeast U.S.
A record of weather patterns in the last decade would be the most useful source in determining the reliability of Punxsutawney Phil's predictions over a number of years. By comparing the groundhog's predictions with actual weather outcomes, you can assess the accuracy of his forecasts and evaluate his reliability as a weather predictor.
Therefore, the Correct Answer is C.