Which of the following is a likely explanation for why invasive species take over communities into which they have been introduced? a) invasive species are less efficient than native species in competing for the limited resources of the environment. b) invasive species are not held in check by the predators and agents of disease that have always been in place for native species. c) invasive species have a higher reproductive potential than native species. d) invasive species come from geographically isolated regions, so when they are introduced to regions where there is more competition, they thrive.