Code 3.30 covers which liquid?

• A. Water
• B. LPG
• C. Liquid nitrogen
• D. Oil

Answer: (D)

Code 3.30 is associated with an oil-type liquid. Oils are a common calibration fluid in measurement verification because their properties—such as density and viscosity—are stable enough to give consistent readings across typical lab and industrial conditions, and they’re readily available and easy to handle. Water is often used as a reference in many contexts, but it’s usually placed under a different category due to its distinct thermal and physical characteristics. Liquid nitrogen is a cryogenic liquid with extremely low temperatures, requiring special handling and separate procedures. LPG behaves as a hydrocarbon that’s typically stored under high pressure and has flammability and safety considerations that put it in a different class as well. So, oil fits the intended category for this code, which is why it’s identified as the correct choice.