The query concerns a specific definition of 'Human geography': "the study of the changing relationship between the unresting man and the unstable earth." The objective is to identify the definer from the provided options.
Analysis of the historical contributions of each individual clarifies the attribution:
The quoted definition of 'Human geography' directly reflects Semple's conceptualization of the evolving bond between humanity and the Earth.
Consequently, the individual who defined 'Human geography' as "the study of the changing relationship between the unresting man and the unstable earth" is: Semple