fluid mechanics

What is the definition of fluid in fluid mechanics

the six forces influencing fluid motion.

Fluid is a substance that:a. flows.b.has the same shear at a point regardless of its motionc.always expands until it fills any containerd.cannot remain at rest under action of any shear forcee.cannot be subjected to shear forces

hypothesis of continuum in fluid mechanics

Newton’s law of viscosity states thata.the shear stress applied to the fluid is directly proportional to the  specific weight of the fluidb.  the shear stress applied to the fluid is directly proportional to the velocity gradient du/dyc.the shear stress applied to the fluid is inversely proportional to the velocity gradient du/dyd.    the shear stress applied to the fluid is directly proportional to the  specific weight of the fluid