It is important to maintain septic systems in order to a. prevent treated sewage from contaminating groundwater b. process human waste into fertilizer c. prevent untreated sewage from contaminating groundwater d. none of the above

c. prevent untreated sewage from contaminating groundwater

Explanation:

A septic system is a household underground wastewater management system. It is a simple designed system for a single building to prevent the wastewater being mixed with the groundwater. It is a simple system which does not require long sewer lines hence prevents the contamination of both air and water. The sewage water in the septic system remains untreated and this can be removed from the septic tank by using pumping mechanism.

On the basis of the above information, c. prevent untreated sewage from contaminating groundwater is the correct option.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).