A is an unaltered document of historical significance created by a 1. witness to the event.
2. newspaper
3. biography
4. sworn testimony
5. primary source

5. primary source

Explanation:

A primary source is an unaltered document of historical significance created by someone who witnessed a historical event.

It represents an original document, without footnotes, which comes from the period you are studying.

These sources are important because they help you go back to the original times and see the source as it is so that you could interpret the event by yourself, without anyone having to interpret it for you.

i would say b. research typically uses a variety of sources

a bad leader