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