Final answer:
Piping for various fluids is primarily identified by color-coding, with additional information conveyed through lettering, line thickness, and symbols according to ANSI/ASME standards.
Step-by-step explanation:
Piping for various fluids is typically identified through a combination of methods for clarity and safety. The correct answer to how piping systems for various fluids are identified is A. By color-coding. However, it's important to note that additional methods such as B. By lettering, C. By line thickness, and D. By symbols are also utilized to provide detailed information about the contents and characteristics of the pipes. For example, color-coding can quickly convey the type of fluid, while lettering and symbols can provide specifics such as temperature range and pressure rating. Line thickness could be used in diagrams to represent physical characteristics like pipe diameter. Industries follow standards such as the ANSI/ASME A13.1 scheme for the identification of piping systems to maintain consistency and safety.