Question

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

Explanation:

The paragraph first introduces the water vortex (whirlpool in bathtub) and then defines a vortex as a mass of fluid in circular motion forming a vacuum in the center. Options a, c, and d are details related to the main definition. Option b gives the core definition of a vortex which is the most important concept in the paragraph.

Answer:

B. A vortex is a mass of fluid that moves in a circular motion to form a vacuum in its center.