Answer:
Step-by-step explanation:
You can assume the source is credible. No one would write to someone while engaging in a war if they were not prepared to state what they wanted to say truthfully. The current letter might be the only one the family gets.
A letter is normally a primary source. A commentary on the letter is generally a secondary source.
The third one is kind of tough. It can be biased. It can be reasoned (it should be).
The third choice is reasoned I guess, but sometimes people wrote very emotionally. We are not Star Trek Vulcans.