I found that the three teachers' predictions were only half right.

That is, there are eight situations.

1: C first, B first, D later.

2: C first, B first, C third.

3: C first, D fourth, D second.

4: C first, D fourth, C third.

5: A comes second, B comes first and D comes second.

6: A comes second, B comes first and C comes third.

7: A second, D fourth, D second.

8: A is second, D is fourth and C is third.

Obviously, the contradiction of 1, 2, 3, 4, 5 and 7 is the same statement.

That is, the first place is _ B, the second is A _, the third is _ _ C _, and the fourth is _ _ D _.