What's the difference between a formal and a vernacular region

What does the word submerged mean in the following sentence? after it rained for three days in a row, the streets were completely submerged.

Nuclear experimentation is a major global issue that affects relationships between countries. describe why countries try to limit the testing of nuclear weapons.

What evidence does the writer give to support his argument about coral reefs? a) he speaks of the activities of coral polyps. b) he describes the composition of the great barrier reef. c) he emphasizes the ways in which coral reefs are fragile. d) he points out the ways that scientists do research on the reefs.