In triangle PQR, the angle Q = 90 degree, PQ = 5 cm, QR = 8 cm. X is a variable point on PQ. The line through X parallel to QR, intersects PR at Y and the line through Y, parallel to PQ, intersects QR at Z. Find the least possible length of XZ
Pick one
A) 3.6 cm  B) 2.4 cm  C) 4.0 cm  D) 2.16 cm  E) 3.2 cm

Rationale: "look at the diagram below : now , in case when qy is perpendicular to pr , two right triangles pqr and pqy are similar : qy : qp = qr : pr - - > qy : 5 = 8 : 10 - - > qy = 4.0 . answer : c ."
Answer: C