Five people (A–E) sit in a U-shape (4 sides). A faces B diagonally. C is second to left of D. E is at a corner. Who sits at the middle of the open side?
Correct: B
U-shape arrangements have three sides with two open ends. A-B diagonal fixes corner positions. C-D's relative position and E's corner placement force open-side middle to be unoccupied by C/D/E/A through elimination.