P, Q, and R are three points in a plane, and R does not lie on line PQ. Which of the following is true about the set of all points in the plane that are the same distance from all three points?
A) It contains no points.
B) It contains one point.
C) It contains two points.
D) It is a line.
E) It is a circle.
해설을 여기서 찾았는데:
https://greprepclub.com/forum/p-q-and-r-are-three-points-in-a-plane-and-r-does-not-lie-1885.html
왜 갑자기 파란선과 빨간선이 나오는건지..