C. 6.81x10^-4
It is negative 4 because the 6 is 4 digits away from the first 0.
Scientific notation has one number and then the decimal place so it can not be A or E.
https://4d4f.eu/content/nascarmartinsville-speedway-first-data-500-live-stream
A a landform that is naturally lower than its surroundings
The water cycle consists of three major processes: evaporation, condensation, and precipitation. Evaporation is the process of a liquid's surface changing to a gas. In the water cycle, liquid water (in the ocean, lakes, or rivers) evaporates and becomes water vapor.
Dams are important because:
They provide water for domestic, industry and irrigation purposes.
Dams often also provide hydroelectric power production and river navigation.
Domestic use includes everyday activities such as water for drinking, cooking, bathing, washing, and lawn and garden watering.
Dams and their reservoirs provide recreation areas for fishing and boating.
They help people by reducing or preventing floods. During times of excess water flow, dams store water in the reservoir; then they release water during times of low flow.