Extended practice at a skill can improve

A) anyone's ability at that skill to the point where he or she becomes an expert.
B) development in the brain areas specific to that skill.
C) other related skills, so someone who becomes an expert at memorizing numbers can as easily memorize faces.
D) overall brain functioning, reducing the likelihood of mental decline.

Extended practice at a skill can lead to improved development in the brain areas specific to that skill. This is supported by research in neuroplasticity, which suggests that the brain can reorganize itself in response to experience. However, becoming an expert at one skill does not necessarily translate to expertise in other unrelated skills, as in option C. While overall brain functioning may improve to some extent with extended practice, there is no guarantee that this reduces the likelihood of mental decline, as in option D.