Final answer:
Relying exclusively on a personal letter for information about a past event can be problematic due to personal biases present in the letter.
Step-by-step explanation:
One problem with relying exclusively on a personal letter for information about a past event is that it would contain personal biases. Personal letters are subjective and can be influenced by emotions, perspectives, and opinions of the writer. For example, a personal letter about a historical event may be written with a specific agenda or intention, leading to a distorted representation of the facts.
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