得ない
文法の解説は英語です。
用法
Used to express the fact that "can't do -" or "there's no possibility to"
V ~~ます~~ + 得ない
例文
あの人が結婚したって本当！？え～！あり得ないよ！
Is it true that he got married? No way! It's not possible!
あの真面目な彼が犯人？そんなことはあり得ない
You think someone as earnest as him is the culprit? That's unbelievable..