What’s the difference between qd and qs?

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.

because the early people found out about it.

answer; people have no objective standard by which to judge themselves;

answer; a variety of simple organic compounds could be spontaneously synthesized from components in earths primitive atmosphere;