According to your friend, what statement is supported by research regarding exercise and Alzheimer's disease?

A) Exercise may reduce the risk of developing Alzheimer's but is not effective in treatment.
B) Exercise may reduce the chances of developing Alzheimer's and may help with treatment.
C) Exercise does not reduce the chances of developing Alzheimer's and is ineffective in treatment.
D) Exercise does not reduce the chances of developing Alzheimer's but may help treat the disease.