Secondary sources

a. provide first-hand testimony and direct evidence
b. interpret and analyze primary or other secondary sources
c. store original reflections and correspondence
d. can only be found in personal collections and private libraries

B. Interpret and analyze primary or other secondary sources

I'm not sure of what to say if it's a, b, c, or d but what I can say is that secondary sources are sources from primary sources. For example, if your dad talked to the president, that's a primary source. If your dad TOLD you that he talked to the president, that's secondary source. Now I think that the answer is a, provide first hand testimony and direct evidence.