Actually, Elrond does no such thing (to my knowledge). However, during the council of Elrond, while he's speaking of the history of the men of Numenor, he says:
And ever since that day the race of Númenor has decayed, and the span of their years has lessened.
In the North after the war and the slaughter of the Gladden Fields the Men of Westernesse were diminished…and the blood of the Númenóreans became mingled with that of lesser men.
So it seems that Numenorian is an actual race. However, he is also a human, (despite his few drops of elven blood). So maybe some modification of the question? Perhaps:
What of the following best describes Aragorn?
He is an Man (Human)
He is an Elf
He is an Númenórian
But then, best is a somewhat subjective term, so maybe that's not the best idea.