Dr. Edward is testing the same individuals repeatedly over time as part of a research study, while Dr. Janice is comparing the performance of different people of various ages at the same time. Dr. Edward is using a research method; Dr. Janice is using a method.

Dr. Edward is using longitudinal research method.

Dr. Janice used cross-sectional research method.

Explanation:

The longitudinal and cross-sectional research methos are observational research methods in which researchers observe their subjects without making any changes in an environment.

The longitudinal research method is the one in which researchers record the changes in traits of the subject or the target audience. The longitudinal research method is the one in which researchers observes their subject over a period of time which may extend upto many years.

The cross-sectional research methos, on the other hand, is the research method in which researchers compare various target audience all at the same time. The researchers perform this research only at one time unlike longitudinal research method.

In the given scenario, Dr. Edward has used the longitudinal research method as he observed the subject over a period of time, whereas Dr. Janice used cross-sectional research method as she studied her various subjects all at the same time.

i am pretty sure it is d.