Practical fluids A. are viscous B. possess surface tension C. are compressible D. possess all the above properties

The correct answer is D. Practical fluids possess all the above properties.

• Viscosity is a measure of a fluid’s resistance to flow. It is caused by the internal friction of the fluid’s molecules.
• Surface tension is the tendency of a fluid’s surface to contract. It is caused by the attraction of the fluid’s molecules to each other.
• Compressibility is a measure of how much a fluid can be compressed. It is caused by the distance between the fluid’s molecules.

All practical fluids have these properties. For example, water is a practical fluid that is viscous, has surface tension, and is compressible.