Answer:
The correct option is a. "increased cortical mass, increased numbers of neurons, increased synaptic connections, increased neurotransmitter amounts, and increased myelination.
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Explanation:
Rodents that have been raised in enriched environments were found to have thicker cerebral cortex containing approximately 25% more synapses in a study conducted by Mark Richard Rosenzweig. This increase in <em>synapses</em> implies in an increase in <em>neurons</em> and <em>neurotransmitters</em>, which also indicates an increase in <em>myelination</em>.
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