One Possible Theoretical Explanation for the Negative Correlation Between Education

One possible theoretical explanation for the negative correlation between education and the rate of Alzheimer's disease in nuns is that

A) education increases "brain work," which in turn increases the density of synaptic connections in the cortex.
B) going to college is also correlated with a family's social economic status,which may be the real cause.
C) nuns who are educated rise in the church hierarchy,and therefore,lead less stressful lives.
D) the nuns are aware of how the brain functions.