"I have a question."

Translation: У мене є питання.

[Vinnfred]

Although many people consider питання and запитання complete synonyms, linguists argue with them on that. The differences:

• Запитання: appeal to someone that needs an answer, request.
• Питання: the problem that needs solving, agenda item, issue

http://ukr-mova.in.ua/assets/uploads/images/Mova_152.png

[AlexIoffe]

В мене є запитання is more natural

[Zonia435615]

Wow! This is the first time I've seen the word 'є' ('is') used in a sentence! And, without a hyphen! That's great! (Now, I feel that Duolingo is actually hearing my concerns!) :) ДЯКУЮ!

[skstudio]

"У мене є" is a kind of set phrase, but even here "є" can be omitted: "У мене питання" (sounds more colloquial).