Stormwater Best Management Practices are about keeping rainfall on the landscape where it falls, slowing it down, and removing pollutants as it moves through the system. Green roofs intercept rainfall on rooftops and create a shallow, vegetated layer that stores water, increases evaporation, and reduces how much runoff leaves the building. Bio-retention areas and rain gardens use engineered soils and plants to infiltrate water and filter nutrients and sediments as runoff passes through. Retention and detention basins provide temporary storage, spreading out the release of runoff so peaks are dampened and pollutants have more time to settle or be treated. Together, these practices actively manage runoff at the source and improve water quality, which is the essence of BMPs for stormwater. The other options describe activities more related to drinking-water treatment or large-scale infrastructure rather than on-site stormwater management.

Coagulation and flocculation focus on removing particles that are too small to settle on their own by first neutralizing their surface charges and then growing them into larger aggregates. A coagulant neutralizes the negative charges on colloids, allowing them to come together instead of repelling each other. Gentle mixing then promotes collisions and growth into larger flocs that can settle in a clarifier or be removed by downstream filtration. This step improves water clarity, lowers turbidity, and reduces the load on filters and disinfection downstream. Removing dissolved salts requires processes like ion exchange or desalination, sterilizing by high heat is a disinfection method, and pathogens are not removed exclusively by filtration—coagulation targets suspended solids and colloids, enabling their removal.

Where water is found at the surface of the land defines the term. Water visible in rivers, streams, lakes, and wetlands is surface water—water that exists on or above the ground and is directly exposed to the atmosphere. This contrasts with groundwater, which is stored underground in soils and rock and is not usually visible. Residence time refers to how long water stays in a system, which is about timing, not location. Eutrophication describes nutrient enrichment and its ecological effects, not where the water sits. So the water you can see in those bodies is surface water.

Electric motors convert electrical energy into motion by using magnetic fields to create torque, which turns the wheels. When a vehicle is driven by an electric motor powered by electricity stored in batteries or supplied from a power source, it is an electric vehicle. This distinguishes it from hybrids (which use both electric and gasoline propulsion), gasoline-powered cars (which run on internal combustion engines), and solar cars (which rely on solar energy to power the drive, though the propulsion is still electric).