Which of the following CANNOT be used as a potable water source?

The most suitable choice regarding sources of potable water is water from a nearby stream. This option is considered unsafe for several reasons. Streams can be contaminated by a variety of factors such as agricultural runoff, sewage discharge, wildlife, and industrial pollutants. Because water from natural sources has a higher risk of containing pathogens and harmful substances, it is generally not held to the same safety standards as treated water supplies.

In contrast, the other options represent sources that can be viable for providing potable water under appropriate conditions. For example, outdoor well water can be safe if it is properly tested on a regular basis to ensure it meets safety standards. Water trucks are often used to transport potable water and can deliver safe drinking water if sourced from a reliable, treated system. Additionally, water from a city water system is routinely treated and monitored to ensure it is safe for consumption.