The correct answer is B: PQ, QR, and PR.
This is because these letters represent line segments. For example, PQ represents the segment that connects the points P and Q. These segments, when considered together, represent a triangle, because the three line segments are connected, therefore B is the correct answer. (Note: A represents the angles of the triangle and C represents the vertices of the triangle; therefore, these answers are not correct).
Hope this helps!