That which cannot be believed

A. Incredible

B. Incredulous

C. Implausible

D. Unreliable

Answer: Option A

Solution(By Examveda Team)

One word substitute is Incredible.

Incredible: impossible to believe.
Incredulous: (of a person or their manner) unwilling or unable to believe something.
Implausible: (of an argument or statement) not seeming reasonable or probable; failing to convince.
Unreliable: not able to be relied upon.