Final answer:
A cross connection is the physical link that allows potable water supply to be connected to a line with potential contaminants, and the correct answer to the question is D. Cross connection. Protection is provided through preventative devices such as air gaps and backflow preventers to safeguard drinking water.
Step-by-step explanation:
The physical link between safe water and dirty water can come from various sources, such as drains, sewers, or other wastewater systems. The correct term for this connection is a cross connection, which is a direct arrangement of piping that allows the potable water supply to be connected to a line which contains a contaminant or pollutant. If there is a pressure change or a back-siphonage situation, contaminants can enter the safe water supply. Devices like air gaps, backflow preventers, and vacuum breakers are installed to prevent such contamination.
For instance, an air gap is a physical separation between the end of a water supply outlet and the flood level rim of a receiving vessel. It is the simplest and most reliable means of preventing backflow as it provides a space for water to fall through without risk of rising contaminants. Vacuum breakers and backflow preventers act as mechanical barriers to prevent water from flowing in the reverse direction. These protective measures are crucial for maintaining the integrity of a public water system and preventing waterborne diseases caused by pathogens present in contaminated water sources.