How would a secondary source be beneficial to a historian studying a particular event?

a. it would eliminate the need for her to evaluate primary sources that have already been analyzed by other historians.
b. it would allow her to determine whether sources are reliable or unreliable without needing to actually read them.
c. it would eliminate the need for her to use any primary sources to support the historical argument she hopes to make.
d. it would her organize her primary sources without having to rely on techniques like historiography or chronological thinking.