What might a coolant leak be indicated by?

Answer: C — Orange stain

A coolant leak is often indicated by an orange stain. This coloration typically comes from the antifreeze that is commonly used in a vehicle's cooling system, which often contains dyes for easy identification of leaks. Antifreeze can be orange, especially certain brands, and when it leaks from the cooling system, it can leave a distinct orange mark on surfaces beneath the vehicle. Other colors, like blue or green, might indicate a leak from other fluids, such as windshield washer fluid or windshield leak sources, while a red stain could point to transmission fluid. A brown stain often suggests an oil leak. Understanding these distinctions helps drivers identify potential vehicle issues and seek appropriate maintenance.