Which term best defines the movement of water inside a container?

Answer: B — Fluid dynamics

Fluid dynamics covers how liquids move and how forces shape that movement inside a container. It looks at the internal flow, including velocity and pressure fields, how viscosity dampens motion, and how boundaries (like the sides of the container) influence currents. When you swirl water, form eddies, or observe how momentum transfers from the walls into the fluid, you’re seeing examples of fluid dynamics in action. The other terms don’t fit as the general study of internal water movement: wave motion describes disturbances propagating on a surface or through a medium, not the complete internal flow; hydraulic action refers to the erosive power of moving water rather than the description of how water moves inside a container; liquid surge isn’t a standard way to denote the study of internal fluid movement.