What Do Discs, Like the Kind Shown in the Accompanying

question 12

Multiple Choice

What do discs, like the kind shown in the accompanying figure, usually measure?

• A) 3.5 inches in diameter and less than one-twentieth of an inch thick
• B) 4.75 inches in diameter and less than one-twentieth of an inch thick
• C) 3.5 inches in diameter and more than one-twentieth of an inch thick
• D) 4.75 inches in diameter and more than one-twentieth of an inch thick

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Definitions:

Bacteria

Microscopic, single-celled organisms found in virtually all environments, some of which can cause disease.

Water Table

The level below which the ground is saturated with water, an important concept in hydrology and environmental science.

Aquifer

Porous rock layer that holds some groundwater.

Surface Water

Water that is found on the surface of the earth, such as rivers, lakes, and ponds, as opposed to groundwater.