Answer
This is a straight line that goes in the z direction.
Work Step by Step
Recall, a locus is the same distance from all of the points no matter what. In a previous problem, we found that the locus of three points in 2 dimensions is a point. However, since the book now wants us to consider three dimensions, the locus is now a line that goes through the point we found in 2 dimensions that is perpendicular to the plane that points D, E, and F are in.
