Final answer:
Option (d) stating that Mark's early temperament and his later personality traits are only moderately correlated is NOT a likely explanation for the continuity of his personality because significant correlations between early temperament and later personality traits are well-documented.
Step-by-step explanation:
The question considers why Mark's personality has remained consistent throughout his life, specifically addressing the continuity of his shyness. Option (d) which states 'Mark's early temperament and his later personality traits are moderately correlated' is NOT a likely explanation for the continuity of Mark's personality. This is because the continuity of Mark's personality can indeed be explained by a correlation between his early temperament and his later personality traits. Multiple research studies indicate that there is a significant correlation between early temperament in individuals and their subsequent personality traits as they mature. Therefore, saying that there is only a moderate correlation when in fact it could be high is misleading and not an accurate explanation for Mark's consistent personality. The other options are more plausible explanations: Genetics can have an influence on temperament (a), parental encouragement or lack thereof can shape social behaviors (b), and choosing an occupation that aligns with one's temperament can reinforce those traits over time (c).