A. 1 → A, 2 → C, 3 → B, 4 → D
B. 1 → E, 2 → D, 3 → F, 4 → A
C. 1 → F, 2 → C, 3 → B, 4 → D
D. 1 → D, 2 → B, 3 → C, 4 → A