Explanation: A longitundinal study is a research design in which the researcher studies and observes the behavior of the same variables (Could be people, traits, characteristics) over periods of time.
In this case, 1- Dr. Samuel wants to study relationship between variables 2- does not wish to establish a cause-effect relationship, but indeed, 3- he is conducting the study over a three year period with the same participants. Therefore, it is a Longitudinal Study.
According to an assessment by the Arlington Institute, in the future, human cloning will raise ethical issues as well as the possibility of extending human life thanks to organ and tissue cloning. This high-impact, low-probability event is an example of wild cards.