Why was irrigation important to Sumer? It led to the invention of the sail. It helped create food surpluses. It led to trade with other city-states. It moved water from mountains to city-states.

It helped create food surpluses

Explanation:

irrigation is about crops, it's to help grow crops where they wouldn't be able to otherwise. So it would help create food surpluses if they were growing more crops.

4 copper and gold, the california gold rush is why im pretty sure.

the quote by walter cronkite contributes to the central idea of the text by supporting the central idea. cronkite argues that what is deemed “right” for and in america may not be good for other countries. this supports the central idea of the text, that the vietnam war was unpopular in america for multiple reasons- including cronkite’s.