Pearl Has a History of Alzheimer's Disease in Her Family

Pearl has a history of Alzheimer's disease in her family. She wants to do everything in her power to try to avoid developing the disorder herself. You tell her she should

A) not worry about it - there's nothing she can do to prevent it.
B) engage in physical exercise throughout her life.
C) play lots of brain games (i.e., cognitive exercise) .
D) engage in both physical and cognitive exercise for the best results.