What is true of matter in ecosystems?
a. the primary productivity of an ecosystem does not depend on the availability of nutrients.
b. living things can recycle elements within an ecosystem as long as decomposers are present.
c. matter flows in a one-way direction with a 10% loss at each move up in trophic level.
d. elements continuously cycle between the physical environment and living organisms.

D.Elements continuously cycle between the physical environment and living organisms.

Ecosystem is encompassing all the life on earth in the physical environment that supports it. An ecosystem involves both the biological (plants, animals, human beings) and non-biological (land, water, soil, and atmosphere) community which interacts as a system. More importantly, the living things are very dependent on the abiotic community since it cannot survive by itself. Every animal, plant and human needs the primary physiological needs of water, food and shelter provided by the abiotic system.  

We are not able to see the stars. light prevents our seeing the stars. i hope it kinda : )