In the maternity ward, four babies have become accidentally mixed. The ABO types of four babies are known to be O, A, B, and AB. The ABO types of the four sets of parents are determined.
Thus, the baby belongs to each set of parents:
| S/NO | Parents | Baby |
| 1 | AB X O | B |
| 2 | A X O | A |
| 3 | A X AB | AB |
| 4 | O X O | O |