Final answer:
A designated Range Safety Officer (RSO) or Range Safety NCO will supervise a misfire with the AT4 during training.
Step-by-step explanation:
The person who will supervise a misfire with the AT4 during training is a designated Range Safety Officer (RSO) or Range Safety NCO. The RSO is a specifically trained individual responsible for ensuring safety on the firing range, which includes the procedure for handling misfires and other hazardous situations. While the highest-ranking officer on-site has overall responsibility for operations, the RSO or Range Safety NCO has the technical supervision of handling misfires professionally and safely.