Angels are messengers from God. The angel Gabriel brings an 'announcement'. Have you ever received a wedding announcement? It requires a response. This is no different. Mary is asked to assent to a truth never expressed before. The angel awaits an answer; it is time for him to return to God who sent him.
Sorry; but I do not see where he awaited an answer to a question that was not asked.
Mary was TOLD what was going to happen: it says so in the text. To spin it so that is NOT what the text says... well...