6 which of the following plays a key role in ones learning and memory?
A the kidneys
B the adrenal hormone
C the stress hormone
D the hippocampus
7 when the levels of cortisol go high ，the hippocampus
A may expand
B may shrink
C may disappear
D may function better
8 according to the passage， when people are under stress，
A the adrenal glands will produce cortisol
B the kidneys will shrink rapidly
C the hippocampus will produce cortisol
D the brain will work more efficiently
9 it app ears that when the hippocampus shrinks sue to high levels of
cortisol， other brain regions
A may change dramatically
B may stop functioning
C may remain unaffected
D may be seriously damaged
10 the research conducted by porter and land field showed that
A the levels of adrenal hormones have nothing to do with brain aging
B changes in the levels of adrenal hormones can affect brain aging
C chronic stress may strengthen ones memory
D the rate of brain aging always remains stable