Final answer:
A fourth point in plane STZ can be named with any letter not already used to denote another point, such as point 'W', provided it lies on the same flat two-dimensional surface.
Step-by-step explanation:
You have asked to name a fourth point in plane STZ. A plane in geometry is a flat, two-dimensional surface that extends infinitely in all directions. Given that we know points S, T, and Z are on this plane, any other point that lies on the same flat surface can be considered a part of plane STZ. To name a new point, we typically use a letter from the alphabet that is not already used to name a point on the plane. Therefore, a fourth point on plane STZ could be named point 'W' as an example. Remember, the specific letter isn't important as long as it's not already in use, and the point lies on the plane STZ.