What type of substances is likely to be stored in a 55-gallon steel drum?

The correct answer is associated with the types of hazardous materials that are commonly stored in 55-gallon steel drums. These drums are frequently used for storing corrosives and flammable liquids due to their robust construction, which provides adequate protection against leaks and environmental hazards.

Corrosives, such as strong acids and bases, can react with many materials, but steel drums are designed to withstand such chemical reactions when properly selected based on the specific substance being stored. Additionally, many flammable liquids require secure storage that minimizes the risk of ignition, and steel drums are effective in containing these hazards. The design of these drums helps prevent leakage and protects the integrity of the materials stored inside.

Furthermore, the other categories of materials listed are not typically stored in 55-gallon steel drums. Explosives require specialized storage that meets strict regulatory standards for safety and containment, making them unsuitable for general drum storage. Biological waste has specific disposal regulations that often do not involve such drums. Lastly, food-grade materials are generally stored in drums specifically designed and certified for food safety, which might not include standard steel drums used for hazardous materials. Thus, B is correct in highlighting the common use of steel drums for corrosives and flammable liquids.