Problems caused by young and old dependents in a country

Explain how the density of ocean water is affected by temperature and how this results in major ocean currents distributing heat away from the equator toward the poles?

Bottle deposit programs are one way to encourage higher recycling rates. explain how they work

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.