Question

Which of the following sources is the most reliable, valid source to include in a historical research paper about the lives of US soldiers fighting in World War I?

a recent news article about a statue being built on a famous World War I battlefield

a teacher's lecture on how World War I soldiers routinely dealt with disease and hunger

your great-grandfather’s journal, which discusses his time in France as a World War I soldier

a history textbook that describes troop formations and weaponry employed by each nation during World War I