D. All of the above ,,,,,,,,,,,,
Firsthand accounts : eyewitness account, letter from a general to his troops, an interview of a war veteran
Secondhand accounts: television documentary, article
I believe that A and B are correct, and if you need 3 than A, B, and D are correct.
Om stuck on the same question i want to say that it's A, C, D, and maybe E. :)