What should the reader emphasize when reading this paragraph?
“Have you ever seen a whirling funnel of water going down the drain of your bathtub? That whirlpool is called a water vortex. A vortex is a mass of fluid that moves in a circular motion to form a vacuum in its center. A vortex works with water much the same way a tornado works with air. A vacuum action tends to draw everything around a vortex toward its center.”

a. whirlpool is called a water vortex
c. A vacuum action tends to draw everything around a vortex toward its center.
b. A vortex is a mass of fluid that moves in a circular motion to form a vacuum in its center.
d. A vortex works with water much the same way a tornado works with air.