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Most U.S. beaches are shrinking or encroaching on the land rather than growing or moving seaward, so the land ofthe U.S. is getting smaller, not bigger. Causes include:A) Global sea level fell as the ice-age ice sheets grew, and this caused rivers to deliver much sediment to thecoast.B) Sea-level rise as the last ice age ended flooded river valleys to form bays, and sediment now is deposited inthese bays rather than being delivered to beaches.C) Global sea level fell as the ice-age ice sheets grew, exposing sand to the attack of large waves during winterstorms, so beaches are now being removed.D) Local regions are rising as fluid injection wells used for waste disposal bulge up the land in many places.E) Dams on rivers have increased sediment delivery to the beaches.Often, landowners along eroding beaches will build groins, which are walls or dams sticking out into the ocean orlake from the beach. Why are these built, and what happens?Sandy beaches: