If an argument or claim is unanswerable, people cannot disagree with it because it is so clearly true.

In economic terms the need to reduce inflation is unanswerable. 从经济学角度考虑，需要降低通货膨胀是毋庸置疑的。

(of a question) without an answer

As to how long this war will last, it's an unanswerable question. 至于这场战争会持续多久，没有人知道答案。