"这是一个很严重的问题。"

Translation: This is a serious problem.

[MarcosRohena]

"a serious question" should also be accepted

[jamesjiao]

No. It should not be accepted. I am surprised no one has objected to this suggestion. 严重的 is used to refer to the severity of an issue. It simply cannot be paired with a 'question'. A serious question refers to a question that's important and not meant to be taken lightly. The difference is actually quite significant. Please do not mislead people if you are not a native speaker and do not fully grasp the nuances.

[Alison920660]

How is it possible to tell whether to translate 問題 as "problem" or "question"?

[Edasaur]

I personally don't think I've ever heard anyone describe a question as 严重

[jamesjiao]

By the choice of the adjective in this case. See my explanation above

[Anon341685]

The trouble is, it's still unclear why it can't be paired.

[jamesjiao]

What's not clear?

[Anon341685]

Why it can't be paired. You state that it can't. You make a connection between serious and important with respect to questions. Then it's left there. One comes away with the impression that there is no particular reason, it's just not the done thing.

[AndriLindbergs]

Why is this not a "very" (很) serious problem?