Oz in Jeopardy!

A quick one today, from the April 14, 2017 game. In the Jeopardy! round, for $400 in the category 2-Letter Words:

Elspeth, the challenger in the middle, got in first and correctly responded, "What is Oz?" Okay, admittedly, that's not the clue I'd give if I were writing that category, but I'm not a Jeopardy! writer, sadly. Anyway, Elspeth's final score reflected the length of the responses in this category, and she ended up finishing in third place.