Diversity among members of a species is important because diversity a
increases the chances of survival under changing conditions.
b
ensures high levels of competition.
c
increases the available ecosystem resources.
d
ensures the variety of reproductive methods for a species.

Diversity among members of a species is important because diversity increases the chances of survival under changing conditions.

If a disease spreads throughout a species, the species with genetic diversity will survive. If the species does not have genetic diversity, they will be wiped out by the disease.

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.