Archaeologists:
a. never work with physical anthropology.
b. study earlier human groups using artifacts and structures as their evidence.
c. are interested in human behavior when it pertains to osteology.
d. only examine complex civilizations that have left architectural ruins.
e. focus primarily on biological imperatives.

B. study earlier human groups using artifacts and structures as their evidence

Explanation:

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.