Which kinds of ruins, left by the Mississippian culture, BEST indicate that late in its existence, its people experienced widespread warfare? A
temples

B
trenches

C
earthen mounds

D
defensive structures

radiant energy is a form of kinetic energy only.(a)

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.