Which of the following statements is true about drilled wells?

The statement that drilled wells are less vulnerable to pollution than shallow wells is accurate because drilled wells typically extend deeper into the ground where the water is more protected from surface contaminants. Shallow wells are more exposed to pollutants from agricultural runoff, septic systems, and other surface-related sources. As drilled wells reach deeper aquifers, they often tap into water that has been filtered by numerous layers of soil and rock, which can provide a natural barrier against pollutants. Additionally, drilled wells are constructed with protective casings that further enhance their resilience against contamination compared to shallow wells.

On the other hand, the assertion that drilled wells are shallow and less polluted does not apply since drilled wells are usually deeper than shallow wells. The claim about having a large cap above ground is not universally true, as well construction can vary. The idea that drilled wells primarily supply water for agricultural purposes is misleading, as they are used for various applications including residential and commercial water supply, not just agriculture. Thus, the resistance to pollution in drilled wells is a significant reason the chosen statement is correct.