comparatives - “…nicer than any other…” vs “…as nice as any other…”

On a practice test, this sentence was given with the instructions to select the correct version:

The English teacher, Mrs. Jensen, is nicer than any teacher in the whole school.

This is obviously a bit nonsensical, because “any teacher” would include Mrs. Jensen, and she can’t be nicer than herself. Two of the four answers were wrong for obvious reasons, but answers A and B were as follows:

A) The English teacher, Mrs. Jensen, is nicer than any other teacher in the whole school.

B) The English teacher, Mrs. Jensen, is as nice as any other teacher in the whole school.

The test claimed that B was the correct answer. (No explanation was given.) Can you please tell me why answer A is incorrect? To me, they seem like two different, but correct, statements.

Thanks!