Final answer:
Compressed gas is one of the three basic types of railcar configurations that firefighters should be able to recognize as it is commonly used to transport hazardous wastes and materials under pressure.
Step-by-step explanation:
One of the three basic types of railcar configurations that firefighters should be able to recognize is compressed gas. This type of railcar is specifically designed to transport gases under high pressure. When dealing with hazardous wastes, it's essential for emergency response teams to correctly identify railcar configurations in order to address potential risks appropriately. These railcars have unique features such as tank car shape, fittings, and placards to indicate the nature of the compressed gas they are carrying. Firefighters must be proficient in recognizing these signs to ensure efficient and safe handling of such hazardous materials.