Read the following context and choose the best option to answer the question.
Context: Rainwater from the roof is collected and funneled into a 25,000 gallon underground cistern . Wastewater from showers , sinks and toilets goes into underground purifying tanks and then into the cistern . The collected water then irrigates the land surrounding the house . Surrounding flowers and shrubs native to the area enable the property to blend into the surrounding rural landscape .
Question: What might this water system be used for ?
Options: 
A. It may be a way to increase utilities .
B. It may be a zero - waste watering system .
C. It may be a way to get access to more water .
D. It may be a way to purify city water .


B