What do ecosystems consist of?

a. biotic and abiotic factors

b. biotic factors only

c. abiotic factors only

Ecosystems mostly consist of both - abiotic and biotic factors. For that reason the answer which would properly address your question would be A - biotic and abiotic factors. Biotic factors are considered to represent the part of nature that are living and affect other organisms while abiotic factors are things which do not affect other living compounds.