In the beginning of the essay “lifeboat ethics”, what subject do environmentalists use as a metaphor for the earth?

Part b: which phrase from the text best support the answers to part a? a. “i don't want to talk to somebody when i go check in at an airport. i just either download the boarding pass to my phone or walk up to a kiosk and get it.” (paragraph 8) b. “you do not have to go far to find someone who disagrees with andrew mcafee, just around the corner to the office of another person at the same university.” (paragraph 11) c. “the set of things that machines do not do like humans is innumerable.” (paragraph 16) d. “you wonder if you're joining that long litany of voices who go down as having made the incorrect prediction one more time, but i think the facts are different this time.” (paragraph 23)