What are barrier islands? why are they so attractive for human development and why are human structures built there so vulnerable?

Barrier island are formed by the deposition of sand along the stretches of main land coast and serve as a barrier for strong storm waves. They are beautiful but unstable hence, human structure development is not safe on these islands.

Explanation:

Barrier island are formed by the deposition of sand along the stretches of main land coast and serve as a barrier for strong storm waves. These islands are not stable and keep on changing their reduced level based on the changing level of sea and long shore level.  

Due to aura of natural landscape, lot of recreational and residential developments are carried out on barrier island but since these islands are not stable due to the shifting sand beneath the island such human structures are not safe.

answer; i believe the correct answer is ( proteins );

coal is not sustainable because it will one day run out.