Fallacy in which a proposition is held to be true just because it has not been proved false, or false just because it has not been proved true is called:

Correct option is C

The fallacy described is known as Argument from Ignorance (also called Ad Ignorantiam). This fallacy occurs when someone claims that a proposition is true simply because it has not been proven false, or it is false because it has not been proven true. This type of reasoning disregards the need for evidence and relies on a lack of disproof as proof.
Information Booster: 1. Argument from Ignorance (Ad Ignorantiam): Assumes that a statement must be true if it has not been disproven, or false if it has not been proven.
2. Fallacy of Composition: Erroneously assumes that what is true for the parts must be true for the whole.
3. Irrelevant Conclusion (Ignoratio Elenchi): Provides an argument that may be logically valid but does not address the issue at hand.
4. Hasty Generalization: Draws a conclusion based on an insufficient or biased sample.