The primary source would be D: Personal interview with an eyewitness.
Primary
source is known data gathered in first-hand basis. A personal interview with an
eyewitness is a first-hand data because the information exactly came from the
person who actually saw what happened on that certain moment. The rest of
choices were second-hand sources. Biography maybe directly from a
person, but another made and wrote the biography. History textbook could be a collection
of hundreds of years texts that meant more sources, same with old newspaper
clippings.
