Turbidity. As your book/question states it is a measurement of cloudiness in water.
I believe the answer is D: It revolves around the family unit.
Answer:
At the stroke of midnight on June 12, 1910, Oklahoma Gov. Charles N. Haskell signed a document declaring the capital of the 2-year-old state was now in Oklahoma City, and the state seal was whisked out of Guthrie for a "wild 30-mile automobile ride" to the new capital.
Explanation: