which of the following is an example of structural mobility? a.) pam and her sister are born poor, but they both attend a prestigious college, secure high-paying jobs, and move into the upper class. b.) william can no longer afford his rent and has to get a roommate because he quit his job as a taxi driver. c.) susan's family moves from an expensive city to a much more affordable one, where they enjoy a higher standard of living. d.) john and his neighbors fall into poverty because the factories in his town are relocating to mexico.