Which of the following describes an advantage that secondary sources have over primary sources for historians

While you didn't really provide the "following" as the comment above me states, in general, the advantage of secondary sources of primary ones is that they perhaps provide a more objective or even just a broader view on a certain topic. While a primary source of the American civil war would be a letter written by a soldier, a secondary source would be a book that describes more letters taken together and discusses possible information regarding them. 

What do you need with? ? try to review those chapters and quiz yourself using flashcards to retain the information