Final answer:
A Water conservation program (D) is the best practice to enable a settlement to become sustainable as it conserves vital water resources. Complementary sustainable practices include planting trees and burning less fossil fuels. Adding water to a recharge area increases the amount of groundwater, benefiting water management.
Step-by-step explanation:
The practice that would best enable a settlement to become sustainable is a Water conservation program (D). This measures such as rainwater harvesting, responsible consumption, and efficient infrastructure, lead to the preservation of water resources which is a vital element for the sustainability of any community. In contrast to options such as increased car sales or fast food restaurants, a water conservation program directly contributes to reducing the environmental impact, conserves natural resources, and supports a long-term ecological balance.
Other effective practices for sustainability not listed in the student's options could include planting more trees, which improves air quality and biodiversity, burning less fossil fuels to decrease greenhouse gas emissions, and implementing responsible agricultural practices such as avoiding excessive soil tilling which helps maintain soil health.
Regarding the question about water resources, adding water to a recharge area would result in an increased amount of groundwater (A). Proper groundwater management is critical for sustainable settlements because it ensures a reliable supply for agriculture, industry, and personal use. It is important to remember that the differential use of natural resources, including water, has a profound impact on the environment's carrying capacity and on urban planning strategies such as the integration of wetlands in subdivision designs.