1) suppose a is wrong in prediction:

Then A is not the first one, and D is the last one.

C is neither 1 nor 4, so C is 2 or 3, and B is the first.

So: from high to low is BCAD or BACD.

2) Suppose that B is wrong in the prediction:

Then B is the last one, which contradicts D's prediction, so the assumption is untenable.

3) Suppose that C is wrong in the prediction:

Then c is the first or last place, which contradicts a and d, and the assumption is not valid.

4) Suppose d is wrong in the prediction:

ABC is all right, and no one comes last, so it is also contradictory, and the assumption is untenable.

To sum up, whether the ranking is BCAD or BACD, A's prediction is wrong.