ANS:A - is frictionless and incompressible

An ideal fluid is frictionless and incompressible. The concept of an ideal fluid is a theoretical construct used in fluid mechanics to simplify analysis. An ideal fluid is assumed to have certain properties:

1. It is frictionless: An ideal fluid is assumed to have no internal friction or viscosity, meaning that it offers no resistance to flow.
2. It is incompressible: An ideal fluid is assumed to have a constant density and is not compressible under pressure changes.
3. It obeys Newton's laws of motion: This implies that it follows the principles of conservation of mass, momentum, and energy.
4. It is not necessarily similar to a gas: Ideal fluids can be liquids or gases, but the key defining characteristics are their frictionlessness and incompressibility.
5. It is not very viscous: In fact, an ideal fluid is assumed to have zero viscosity, which means it does not exhibit any resistance to flow due to internal friction.