Which of the following would best describe the color of DEF?

The correct answer indicates that Diesel Exhaust Fluid (DEF) is essentially a clear liquid. DEF is composed of 32.5% urea and 67.5% deionized water, and its clarity is important as it needs to be free of contaminants and impurities to function effectively in reducing nitrogen oxide emissions in diesel engines.

While some fluids might have distinct colors for identification purposes, DEF does not, and it is advisable to keep it that way for ensuring quality and proper application in a vehicle's SCR (Selective Catalytic Reduction) system. It's crucial for technicians to recognize this characteristic of DEF, as understanding its proper handling and storage conditions can prevent contamination that may hinder performance or cause damage to the SCR system.