Why is an article written about a famous explorer considered a secondary source

Gettysburg address question. what is the best line from the address? why do you think so?

Which statement is correct ? a. aborigines were the first people to settle australia and new new zealand. b.aborigines were the first people in australia,and maori were the first people in new zealand c. the maori were the first people in australia, and aborigines were the first people in new zealand . d.the aborigines and the maori descended from the polynesians, the first people to settle australia and new zealand.

Which of the following items would serve as a primary source for a historian studiying the american civil war