What is a key difference between the popular spaceship framework and garrett hardin's lifeboat framework? a. the spaceship metaphor suggests that resources will eventually run out for everyone; the lifeboat metaphor suggests that resources will never run out. b. the metaphor of the spaceship portrays earth as a small system with few humans in it; the metaphor of the lifeboat portrays earth as a large system with many humans. c. the spaceship metaphor suggests that humans must share resources to survive; the lifeboat metaphor suggests that some humans must hoard resources. d. by comparing the earth to a spaceship, environmentalists argue for a technological solution; by comparing the earth to a lifeboat, hardin argues for a natural solution.