Final answer:
The researcher's decision to study changes in depressive symptoms of people before and during the pandemic by taking advantage of the pandemic is an example of a natural experiment.
Step-by-step explanation:
The researcher's decision to study changes in depressive symptoms of people before and during the pandemic by taking advantage of the pandemic is an example of A) Natural Experiment.
A natural experiment occurs when a researcher capitalizes on naturally occurring events or conditions to study the effects of an independent variable on a dependent variable. In this case, the pandemic serves as the naturally occurring event, and the researcher is examining the change in depressive symptoms as the dependent variable.