Picture yourself on a tranquil tropical beach. The late afternoon sun warms your face, chest and legs. Squeaky clean sand sifts through your salt-flavored fingers. Your mind thinks little further than the splashing of waves on the shoreline and the light flickering off shoals of little fish whizzing around in the crystal clear shallows. That’s the scenario on many Pacific islands, where the sands, in an inevitable process, are always shifting, therefore ... .

Which of the following sentences correctly completes the idea of the passage?