How did the Nile help unite Upper and Lower Egypt?

Explanation:

Menes sent an army down the Nile and defeated the king of Lower Egypt in battle. In this way Menes united the two kingdoms.

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.