While researching the origins of a community, a student discovers a conflict when comparing data obtained from different sources. Which of the following sources is considered the most reliable?
A. An editorial commemorating the hundredth anniversary of the community's founding
B. Famous anecdotes in pamphlets distributed by the local chamber of commerce
C. Published letters written by one of the community's original settlers
D. A recent biography of the life of the individual credited with founding the community
