Name of item that is a secondary source

Discuss the ways in which the northern and southern economies and social customs differed in the decade prior to the civil war. why are they characterized as having “two distinct societies”?

What was the main cause of the russian revolution? a. the protests against the war with poland b. the tremendous war losses of world war 1 c. the protests against the treaty of brest- litovsk d. the losses dictated by the treaty of versailles

Who did the first work in creating vaccines