It is possible that Native Americans originally have migrated to the Western Hemisphere over a bridge of land that once existed between Siberia and Alaska.
444.It is possible that Native Americans originally have migrated to the Western Hemisphere over a bridge of land that once existed between Siberia and Alaska. (A) have migrated to the Western Hemisphere over a bridge of land that once existed (B) were migrating to the Western Hemisphere over a bridge of land that existed once (C) migrated over a bridge of land to the Western Hemisphere that once existed (D) migrated to the Western Hemisphere over a bridge of land that once existed (E) were migrating to the Western Hemisphere over a bridge of land existing once