One-word substitution (believability): Choose the adjective that means impossible to believe; beyond credibility. Context: Do not confuse with ‘‘incredulous’’ (a person's skeptical attitude) or related terms like implausible/unreliable. Instruction: Select the most accurate single-word substitute.

Given data

• Sought meaning: that which cannot be believed.
• Potentially confusing lookalikes: incredulous, implausible, unreliable.

Concept / Approach
‘‘Incredible’’ describes something unbelievable. ‘‘Incredulous’’ is a person who is skeptical; ‘‘implausible’’ suggests unlikely but not strictly unbelievable; ‘‘unreliable’’ means not dependable.

Elimination
Incredible — cannot easily be believed; correct. ✅Incredulous — skeptical person's attitude; wrong part of speech/meaning. ❌Implausible — lacks plausibility; weaker than unbelievable. ❌Unreliable — not trustworthy; unrelated to belief content. ❌

Usage
‘‘The tale was so incredible that no one accepted it.’’

Final Answer
Incredible