The correct answer to the Chairs quiz is a chair is a One Leg, Prep Level stunt. The glossary definition of chair begins with “A prep level stunt …” making it clear a chair is prep level from a rules point of view.
The one leg or two leg part is a little trickier and requires looking at the glossary definition of Stunt. It says:
A stunt is determined to be “One Leg” or “Two Leg” by the number of feet that the top person has being supported by a base(s). If the top person is not supported under any foot, then the number of legs in which the top person is supported will determine if it is a “One Leg” or a “Two Leg” stunt.
Exception: If a top person is in a non-upright position, which is not supported under any foot, then the stunt will be considered a “Two Leg” stunt.
Since a chair is not supported under either foot we move to the number of legs supported. The chair being supported on 1 leg, at the ankle, makes the chair a One Leg stunt, making One Leg, Prep Level the correct answer to the quiz.
This ruling and explanation are based on the 2016-17 version of the rules dated August 31, 2016.