Questions: Which of the following is a natural cause of groundwater pollution? landfills rocks runoff

The answer is the second one: rocks.

Explanation for each option:

1. Landfills: Landfills are typically man-made sites where waste is disposed of. They can cause groundwater pollution through the leaching of contaminants, but this is not a natural cause. Therefore, this option is incorrect.

2. Rocks: Certain types of rocks can naturally contain minerals or elements that can leach into groundwater, causing pollution. For example, rocks containing arsenic or fluoride can lead to natural groundwater contamination. Therefore, this option is correct.

3. Runoff: Runoff is typically associated with water flowing over the surface of the land, often carrying pollutants from human activities such as agriculture or urban areas into water bodies. While it can contribute to groundwater pollution, it is not a natural cause in the context of this question. Therefore, this option is incorrect.

In summary, rocks are a natural cause of groundwater pollution due to the minerals they may contain.