Why do mapmakers use imaginary lines on maps and globes?

This word for a bug or malfunction was popularized in the 1962 book into orbit by the mercury astronauts

What structure on the south african coast has a range of 63 km and releases flashes every 30 seconds?

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.