Chemical equation should be balance why

How are the high islands of the pacific formed? a. by connected coral reefs called atolls b. by lagoons c. by moving glaciers d. by underwater volcanoes

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.

What is an additional type of erosion found at the coast? what does it mean?