Which type of cargo can never be carried on a bus?

The reason irritating materials or tear gas cannot be carried on a bus is due to safety regulations and the potential risk they pose to passengers and the driver. These substances are classified as hazardous materials because they can cause harm or discomfort if released, leading to serious safety concerns in a confined space like a bus. Therefore, transporting them is strictly prohibited to ensure the safety of everyone on board.

In contrast, small arms ammunition labeled ORM-D, hospital drugs, and food items may be permissible under certain conditions. For example, ORM-D items can be transported in limited quantities for personal use, hospital drugs can be carried under strict guidelines, and food items are typically allowed as long as they do not pose any health risks. The regulations surrounding hazardous materials are designed to prevent situations that could lead to emergencies or injury, thus highlighting the necessity of avoiding transport of substances like irritating materials or tear gas.