"Can you ask him?"
Translation:Kan du spørre ham?
If the object of the sentence is a form of “spørsmål”, you should use the verb “stille”. In pretty much all other cases you should use the verb “spørre”, in particular when you want to express that you are asking a person. Thus:
Jeg spør ham. (I ask him.)
Jeg spurte min mor. (I asked my mother.)
Jeg stiller et spørsmål. (I ask/pose a question.)
If the direct object is “spørsmål”, you should use “stille”, even when there is also a person who is asked:
Jeg stiller ham et spørsmål. (I ask/pose him a question.)
One occasionally hears the expression “spørre et spørsmål“, but it’s generally considered incorrect, and you should avoid it.