In general, chemicals enter ecosystems through which two spheres?
(a) atmosphere and hydrosphere (b) biosphere and lithosphere (c) atmosphere and lithosphere (d) biosphere and hydrosphere

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.

earthquake fault lines