What substance is likely to adsorb pesticides effectively?

The correct answer, clay, is a material known for its fine particles and high surface area, which make it particularly effective in adsorbing pesticides. Adsorption refers to the process where molecules adhere to a surface, and clay minerals often have a significant amount of charged sites that attract and hold onto pesticide molecules. This property is vital in agricultural and environmental contexts to mitigate the risks of pesticide runoff into water bodies and to manage residues in soil.

In comparison, sand, while it does have some ability to adsorb substances, has larger particles and lower surface area, which limits its effectiveness in holding onto pesticides. Water is not capable of adsorbing pesticides efficiently; instead, it dissolves many types of pesticides, potentially leading to leaching and contamination of groundwater. Air also cannot adsorb pesticides in the way that solid media can, as it does not provide a substantial surface area for pesticide molecules to bind. Therefore, clay is the most efficient choice for adsorbing pesticides due to its unique physical and chemical properties.