Answer:
longitudinal study
Step-by-step explanation:
A longitudinal study refers to an observational form of research in which information is collected periodically over a period of time for the same topics. Longitudinal research programs can be stretched over years, or even decades. In this study, the same persons are examined during the time of the study. These studies are popular in psychology, sociology, where researchers are able to analyze changes over a long span of time. As per the question, the researcher wants to gather data for an extended period and therefore it should fall under the category of the longitudinal study.