Is there a single word that encapsulates the idea of a question and answer pairing or grouping? So far, google has turned up nothing helpful on the topic. Naturally, reviewing the options for both questions and answers in a thesaurus turns up nothing because the alternatives are similar to the idea of one or the other, but not both combined.
This might be esoteric and on the edge, but we don't really know the context for OP's query:
What came to mind was a "challenge". When you can't remember your password on your banking site, as an example, they will give you a "challenge", a "challenge question", or a "security question" (I've heard all three). They would seem different from a regular question in that there is supposed to be only one acceptable answer paired to the question portion of the challenge. A soldier on guard duty might also issue a challenge that would need to be returned with the correct paired answer.
Just an idea. "Challenge" was single word as requested. Like I say, we don't have a lot of information.