Which Person Is at the Least Risk for Developing Dementia

Which person is at the least risk for developing dementia?

A) Sara, who graduated high school and is a clerk at a gas station.
B) Susan, who did not graduate from high school, but is a successful salesperson at a local insurance agency.
C) Sandi, who graduated from college and is a manager at a rental car company.
D) Suri, who graduated with a Ph.D.and does research on treatments for autism.