19. What is the term for resistance to flow? . I Plasticity 2. Viscosity 1. Fluidity 4. Elasticity

## Step 1<br />The question is asking for the term that describes the resistance to flow. This is a concept in fluid dynamics, a branch of physics.<br /><br />## Step 2<br />The term that describes the resistance to flow is viscosity. Viscosity is a measure of the internal friction of a moving fluid. It is the force that opposes the relative motion of two layers of fluid that are moving at different velocities.<br /><br />## Step 3<br />The other options provided, plasticity, fluidity, and elasticity, do not describe the resistance to flow. Plasticity refers to the ability of a material to undergo significant deformation before rupture. Fluidity refers to the ability of a substance to flow freely. Elasticity refers to the ability of a material to return to its original shape after being deformed.