What is the production possibilities frontier?
a) the points on a production possibilities graph that show an underutilization of resources
b) the points on a production possibilities graph that show the total revenue of an economy
c) the line on a production possibilities graph that shows the maximum possible output
d) the line on a production possibilities graph that shows how production increases as new technologies are introduced

Read this passage from "the city without us" by alan weisman: which statement best explains how the structure of the passage supports the author's purpose? a. the passage traces several events in the order that they will occur to highlight how nature conquers human civilization. b. the passage shows that natural forces such as an absence of predators and an increase in the squirrel population can lead to destructive results. c. the passage shows that natural forms such as an absence of predators and human hunters can lead to the reforestation of new york city. d. the passage identifies how two natural forces are co-dependent - the deforestation of new york and the extinction of squirrels.