A scientist is studying a volcano that is made of alternating layers of liquid lava and explosive materials such as ash. What type of volcano is it

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.