Which liquid has the highest viscosity?

water

acetone

oil

salt water

Answer is: oil has the highest viscosity.

The viscosity of a fluid is a measure of its resistance to gradual deformation by tensile stress and shear stress.

The dynamic viscosity of water is 0,890 cP (centipoise) at about 25 °C.

The dynamic viscosity of acetone is 0,306 cP at about 25 °C.

The dynamic viscosity of olive oil for example is 81 cP at about 25 °C.