Primary sources are direct from someone or something who experienced a certain event in history. These are not the opinions of others, or compiled after the fact. They are true, first-hand accounts or evidence about an event.
The options that meet this definition are A. Diaries, C. Artifacts (if they are found and date back to a specific incident), D. Human remains. All of these represent a source directly linked to a time period, rather than based on later reflection.