Which of these is an example of an overqualified individual?

a$.$

Sam, who was a shift supervisor but took a job as an entry$-$level medical tech after completing a $2-$year degree.

b$.$

Inga, who was the director of human resources but now is a receptionist after her position was eliminated.

c$.$

Toby, who was the Director of Finance but now is the CFO.

d$.$

Marco, who worked on the assembly line but now is the shift supervisor.