According to the Muslim Geographer Ali al Masoodi in what year did Muslims make contact with the Americas? 900 AD

1492 AD

1200 AD

911 help

People keep spending additional units of a particular resource on a want until their marginal benefit is  decreasing withgreater thanless thannot affected by  their marginal cost.

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.

Which of the following regions suffers the most from acid rain? a. the area around vancouver c. the area below atlanta b. the area below detroit d. the area above montreal