案例分析题 According to the passage, which group of people seem to age slower than the others

A．branches of knowledge studied in a school
B．something to be considered
C．persons experimented on
D．citizens in a country

A．our brains shrink as we grow old
B．the front section of the brain does not shrink
C．seventy-year-olds have better brains than sixty-year-olds
D．brain contraction may vary among people of the same age