The correct answer is:
D. Primary sources are created during a particular historical era, and secondary sources are created by studying primary sources.
Explanation:
Primary sources are those that were created during the historical time of the research, or were told, written or recorded by a person that participated, witnessed or lived during that particular time and event. Primary sources are often told by a particular perspective and reflect the personal point of view of an individual. On the other hand, secondary sources are those that analyze a historical event from an objective point of view, secondary sources often compare and study primary sources, reliable secondary sources are based on primary sources.