Why is a shell considered to be biotic? because it is found in the biosphere because it was alive because it came from something living because it is not living

C, because it came from something living

Explanation: The definition of biotic is of or relating to an environmental factor that is living or that came from something that was once living. Specifically, on the part where it says that it "came from something that was once living". Thus, making it living or biotic.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.

c. live where it’s cold and icy