Answer: B. Non-viscous and incompressible
An ideal fluid is non-viscous and incompressible
A fluid that is incompressible and has no internal flow resistance is the ideal fluid (zero viscosity). Additionally, ideal fluid particles don't rotate around their centres of mass (irrotational). Although the individual fluid particles are irrotational, an ideal fluid can flow in a circular pattern.
Even when the fluid is subjected to external pressure, the density of a perfect fluid never changes. This is the compressibility attribute. Therefore, ideal fluids are incompressible.