Final answer:
Charlotte's rise from a lower-class background to CEO demonstrates upward social mobility within a class system, highlighting her ability to improve her social status through her career achievements.
Step-by-step explanation:
Charlotte's story from a lower class family in rural Pennsylvania to becoming the CEO of a large corporation demonstrates social mobility, specifically upward mobility within a class system. Unlike a caste system, where social status is fixed, a class system offers the opportunity to move to a higher class through hard work, seizing new opportunities, or achieving success in one's career. Charlotte exemplifies this by rising from a humble starting position in the mail room to the executive level of a company, thereby demonstrating that, despite her lower-class background, she was able to overcome barriers and increase her social status.