Research on men's and women's brains indicates that :

Research on men's and women's brains indicates that
 
  A) men have a larger corpus callosum.
  B) males are left-brain dominant; females are right-brain dominant.
  C) men's and women's brains are identical.
  D) males' and females' brains may develop or be structured differently.

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A difficulty in looking for sex differences in the brain is that
 
  A) human brains remain the same as people age.
  B) scientists do not yet fully understand the way in which the structure of specific parts of the brain affect how they function.
  C) human brains are identical to the brains of animals.
  D) none of the above