The passage suggests that a geographer would consider a city's soil type part of its ______.

A．summarize past research and introduce a new study
B．describe a historical period
C．emphasize the advantages of one theory over another
D．define a term and illustrate it with an example

A．The development of trade mutes through United States cities
B．Contrasts in settlement patterns in United States
C．Historical differences among three large United States cities
D．The importance of geographical situation in the growth of United States cities