The correct answer is B) longitudinal study.
The researcher most likely conducts the research using a longitudinal study.
A researcher wants to know if the same parenting style used effectively on urban children at a young age will remain as effective as the same children get older. The researcher most likely conducts the research using a longitudinal study.
A longitudinal study is observational. The researcher never interferes with the subject of study. The characteristic of this type of study is that the researcher maintains the observation for a longer period of time. It could be for many years in order to follow up the object of study. Hence, he can detect changes, improvements or developments so the researcher can establish a sequence of events.