Which of the following is a primary source of arsenic?

The primary source of arsenic being the erosion of natural deposits found in rocks and soil is accurate because arsenic is a naturally occurring element that can be found in the earth's crust. As rocks and soil erode over time due to weathering processes, arsenic can be released into groundwater and surface water. This natural release can lead to increased arsenic levels in drinking water sources, especially in areas where the geological conditions are conducive to higher concentrations of arsenic.

In contrast, the other choices involve various human activities or pollution sources. Industrial wastewater from agriculture may contain many contaminants, but it is not recognized as a primary source of arsenic in the same way that natural deposits are. Urban runoff can carry various pollutants, but it tends to focus on materials associated with urban infrastructure rather than the naturally occurring arsenic. Discharges from chemical weapon storage sites may involve a range of hazardous substances, but these sites do not provide a consistent or primary source of arsenic compared to natural geological processes.