In very early human history, complex sanitation systems were not needed because settlements were usually very small, like the vi
llage shown below.
However, as cities became larger and population densities increased, one major advancement was the development of _______, which helped to channel wastewaters away from human populations more effectively than in the past.
A.
fountains
B.
water towers
C.
sewer systems
D.
dams
However, as cities became larger and population densities increased, one major advancement was the development of _______, which helped to channel wastewaters away from human populations more effectively than in the past.
A.
fountains
B.
water towers
C.
sewer systems
D.
dams
2 answers:
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