Answer:
In this scenario, Jeremy defined depression using a:
d) operational definition.
Step-by-step explanation:
Operational definition is simply the way a researcher decides to define and measure something. In this case, Jeremy has a certain definition of depression that includes specific behaviors: panic attacks, hunger, and headaches. By measuring those behaviors, he determines whether participants are depressed or not. Another researcher could have a different operational definition for depression and measure, instead, how often in the past 6 months the participants have displayed anger or shown low energy levels, for example.