Sounds travel through the air with an average speed of 340 m/s. A girl drops a rock from a bridge to the water 20m below. After the rock strikes the water, how much time will be required for the sound of the splash to reach the girl's ear?

Nps pollution is caused by rainfall or snowmelt moving over and through the ground. nonpoint source pollution can include: excess fertilizers, herbicides and insecticides from agricultural lands and residential areas. oil, grease and toxic chemicals from urban runoff and energy production

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.

Not what goes around on earth but the universe too.