Answer:
b) To provide first-hand knowledge of past events from a participant.
Step-by-step explanation:
In Mandatory Military Service in America, the author tells us about the recollections of a Vietnam veteran. The purpose of doing this is to provide first-hand knowledge of past events from a participant. This veteran participated in the Vietnam War, and this means that he has experienced the war first-hand. This leads him to have a type of knowledge that other people do not have, and that could prove important to the analysis the author is trying to make.