Which of the following choices is a hazard class you are not allowed to smoke around?

The correct answer encompasses all of the listed classes—oxidizers, flammables, and explosives—indicating that smoking is prohibited around any of these materials due to their inherent risks.

Oxidizers, such as certain chemicals that can enhance the combustion of materials, can cause fires to start more easily or burn more intensely than they otherwise would. Therefore, smoking near these substances poses a significant risk.

Flammables, which include a wide range of liquids, solids, or gases that can easily ignite and burn rapidly, are also dangerous to be near when smoking. The act of smoking could introduce a spark or an open flame, leading to potential ignition.

Explosives are substances that can undergo a rapid chemical reaction, producing a large volume of gas and heat in a very short time. The introduction of an ignition source, such as a cigarette, can trigger a catastrophic explosion.

Given the risks associated with all three classes, it is clear that smoking is strictly prohibited around any of these materials to ensure safety and prevent dangerous incidents.