Which of the author's conclusions is best supported by the text?

A.

The clerk probably laughs, knowing you are joking.
B.

Today, we should be grateful that we have laws to protect our water supply.
C.

It seems that they understood that plumbing was the way to keep water somewhat clean.
D
.

Today conserving water is not a concern, except in times of drought.

C. It seems that they understood that plumbing was the way to keep water somewhat clean.