Final answer:
The minimum tread depth for the tires of a bus, except for those at the front, is 4/32 of an inch, which is option C.
Step-by-step explanation:
The minimum tread depth for the tires of a bus on any wheel other than those at the front is 4/32 of an inch. This requirement is set by transportation safety regulations to ensure that vehicles maintain adequate traction and safety on the road. Tread depth plays a critical role in the vehicle's ability to grip the road, especially in adverse weather conditions.