Final answer:
The most prominent concern in the research study is 'B. restriction of range', as sampling from an athletics club can lead to a non-representative sample with limited variation in physical activity, thereby obscuring the true relationship between physical activity and weight in the general adult population. The correct answer is option b.
Step-by-step explanation:
The most prominent concern regarding the research study that examines the correlation between physical activity and weight among adults is B. restriction of range. When a researcher samples individuals from a local athletics club who frequently exercise, the variation among participants in terms of physical activity levels is limited compared to the general population.
This can result in a narrower range of physical activity levels within the sample, which can potentially skew the results and not accurately reflect the true nature of the relationship between physical activity and weight in the broader adult population.
Other options such as outliers, reliability, and violation of the homogeneity of variances assumption are also potential concerns in research studies, but restriction of range is the most applicable to this scenario. It's crucial for researchers to consider this when designing studies and interpreting results.