Answer: Point R
===================================================
Step-by-step explanation:
The term "coplanar" means "points that are in the same plane".
Points A, S and U are all in the base plane. Think of this as the floor of the pyramid, so to speak. These three points are with C, D, and E, which are also on the base plane or floor plane. So we can say that all of these points are coplanar.
In contrast, point R is not on the floor plane. It's higher up. So that's why R is not coplanar with points C,D,E.