Matter in an ecosystem a. flows only one way b. is part of an open system c. is eventually lost as heat d. is broken down into chemical nutrients

B. is part of an open system. this should be correct.

Bis part of an open system

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on