Decomposers are an important part of the ecosystem because
A. they return moisture to the soil
B. they return needed nutrients to the soil
C. they help spread plant seeds

the answer correct answer would be B. :)  

Explanation:

Without decomposers, dead leaves, dead insects, and dead animals would pile up everywhere. ... Thanks to decomposers, nutrients get added back to the soil or water, so the producers can use them to grow and reproduce. Most decomposers are microscopic organisms, including protozoa and bacteria. (credits to google for explanation)

materials water oxygen those are the things i can think of in this moment.

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.