Answer:
He used an interpreter, someone who could speak both languages. Or an adviser.
secondary sources are: books, newspapers, pamphlets and encyclopaedias. Secondary sources involve generalization, analysis, synthesis, interpretation, or evaluation of the original information so i would say D. a series of correspondence between former United States presidents Thomas Jefferson and John Adams
Not:
Invasion of Poland
Nazi-Soviet Non-Agression Pact
Pearl Harbor
Munich Conference
The rest are all associated with WW1
hope this helps