How has the field of geography evolved from the 19th century to today?
a. the advent of gps has limited geographers understanding of the world.
b. geographers accept the theory of environmental determinism more widely than they in the past.
c. since the advent of gis, geographers no longer use single-layer maps.
d. geographers now focus more on theoretical principles than on practical applications of geography.
e. the use of scientific method of mathematical reasoning has resulted more accurate maps over time.