An advantage of prototyping is tied to the fact that user change over time.

i believe the answer is:   psychological  experiment

in this experiment, wilhelm wundt became the first person that implement scientific method in analyzing the pyschological phenomenon.

due to this result, wilhelm wundt also able to make psychology to be acknowledged as a separate scientific field from biology.

all cities have a governor

all cities are in states or provnies then country

all cities have people

difference

some are rich

some are poor

some are average