I added a screenshot with the complete question along with the diagram.
Answer: point Z
Explanation: First, let's consider the plane containing WXY. Taking a look at the diagram, we can note that this plane is the base of the prism. Now, the base of the prism is given as a rectangle named WXYZ. All the points of the base lie on the same plane. Based on the above, point Z would be the fourth point lying on the plane WXY
