All the characters in the novel are fictitious.

Answer: Option C

Unreliable : not able to be relied upon.
Unbelievable : not able to be believed; unlikely to be true.
Unreal : imaginary or illusory.
Real : actually existing as a thing or occurring in fact; not imagined or supposed.
Fictitious : not real or true; imaginary or fabricated.

Synonym of Fictitious is Unreal