Final answer:
Smith and Smoll's studies demonstrate that positive coaching behaviors play a significant role in athlete development, which aligns with research showing small but important effects of mentoring on performance and career outcomes.
Step-by-step explanation:
The results from Smith and Smoll's studies on coaching behaviors indicate that positive coaching has a significant impact on athlete development. Therefore, the correct answer from the given options would be B. Positive coaching behaviors have a significant impact on athlete development. These studies align with other research that suggests mentoring and coaching can have a positive but small effect on various outcomes, including performance, motivation, satisfaction, career advancement, compensation, and job promotions.