Which text is valuable for gaining context about a historical event but is unreliable as evidence

C). Historical Novel.

Explanation:

A Historical Novel is defined as the literary genre belonging to fiction that is set in a historical period and narrates the events or social conditions of the era with a realistic touch that allows the readers to connect with it. As per the question, 'historical novel' is esteemed for knowing the context of a particular historical event(background or the circumstances in which the story is set in) but it is mutable as the evidence to substantiate a claim. Thus, option C is the correct answer.