Two friends are discussing concepts for a new fantasy story:
A: There exists a magical mirror that leads to a mirrored universe. In this universe, people drive on the left side of the road, and you were a king who was adored by everyone! Unfortunately, you from that universe died in an accident, but that also means that you from this universe can enter it and take his place and live forever as king!
B: But A, haven't you pay attention in _______________ class? You cannot live in the mirror world forever because _______________
What is the problem?