Roberto wants to write a short piece to share his effective study techniques with his friends and other students. The best way to communicate his ideas would be through a(n)

the first part is ocean

explanation:

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.

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.