The idea that regions are fluid means that
a.
earth’s surface is floating on a hot magma layer
b.
a region cannot support life without a source of freshwater
c.
a region is difficult to define because it is influenced by people's perceptions and perspectives
d.
formal geographic and political boundaries define a region

The idea that regions are fluid means that a region is difficult to define because it is influenced by people's perceptions and perspectives. The correct option among all the options that are given in the question is the third option or option "C". A region can always increase or decrease depending on the perception of a person as a liquid can change shape depending on the container in which it is kept.

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