Although most urban dwellers in mexico must struggle to survive, most mexicans come to cities of the opportunity to
a)own small parcels of land
b)become members of the upper class
c)work on latifundios
d)work and go to school

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.