Dangerous substances in an ecosystem that are harmful to its organisms are: A sediments. B scavengers. C pollutants. D overpopulation.

C pollutants

Explanation:

Pollutants are dangerous substances in the ecosystem that are harmful to its organisms. They are contaminants and effluents that leads to pollution in the environment.  

There are different types of pollutants. Most of them are introduced into the environment by anthropogenic activities. Also, some natural events also introduce these pollutants into the environment. These materials pose huge health risks to living organisms. They can render the environment unfit for life.

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.

That would be the corect answer hope this