What type of source is also known as secondhand information?

A type of source that is known as secondhand information is a secondary source.

Explanation:

A primary source means that it is a source directly related and more reliable that a secondary source which is related but has gone through other people or things and is not as directly related.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain

(b) britain had a much larger navy than the u.s.

(d) the u.s. had a small army compared to britain.