9. what are "habitat islands,” and how do they occur?

Habitat islands are basically patches of suitable habitat types, which is surrounded by unsuitable habitats.

Once humans clear an area for development, they remove or destroy the resources organisms they must have to survive.

There's your answer! Hope this helped.

~sofia

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.