Synonyms for Unanswerable:

adj.

final (adjective)
definite.
irrefutable (adjective)
incontestable.
undeniable (adjective)
true.
valid (adjective)
authentic.

n.

firm, factual, true, realistic, definitely, definite, objective, authentic. Rapid-fire, unasked, unanswered, interrogative, loaded, open-ended. unanswerable (noun)
incontestable, incontestible.

Other synonyms:

open-ended, unanswered. interrogative, loaded. Other relevant words:
incontestable, factual, interrogative, open-ended, loaded.