The eyewitness testimony was incontrovertible.

Answer: Option A

Unquestionable : not able to be disputed or doubted.
Disputable : not established as a fact, and so open to question or debate.
Unacceptable : not satisfactory or allowable.
Debatable : open to discussion or argument.
Incontrovertible : not able to be denied or disputed.

Synonym of Incontrovertible is Unquestionable