The combined genetic information of all members of a particular population forms a
a. bottleneck
b. gene pool
c. gene flow

true, i don't really know what you're asking but from the info you provided im guessing the answer is true.

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.