Let's start by examining the different choices.
1. Choice(x,y) =x, This essentially means that x is chosen over y, which gives us some direction. It has become pretty much obvious that x is revealed preferred to y.
2. Choice(y,z) =y, This means y is revealed preferred to z. The set has not taken x into consideration which helps us conclude without any confusion.
3. Choice(z,x) =z, z is revealed preferred to x, which is absurd. Check the figure below, it violates the weak axiom of revealed preference.
Going on to comment about the choice from (x,y,z) doesn't make sheer sense. So, the answer must be a) Ms. A violates the weak axiom of revealed preference.
Correct me if I'm wrong. Thanks =)