Our third rule tells us that wither W or Z must not be selected, it is impossible that both W and Z are in. Lets look at what would happen if X and Y are both not selected.
In: Out: X, Y
Since we know that we must have at least two of the topaz stones in, we know that we have W and Z in
In: W, Z Out: X, Y
Since we know that W and Z cannot both be in, it is impossible that X and Y are both out, so the answer is D.
