what does EC mean, im trying to turn in my extra credit for my high school online classes(i dont know if its like only a high school thing or not) and next to the assignment name it says "EC DO NOT TURN ANYTHING IN" ??

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.