The matching up of rock layers from one area with those in another area is known as

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.

Find the area of the shaded region.

Which barrier to economic development is shown in the following examples?