It is asking about the preferred delivery method. "우편 등기 택배 중 어떤걸로 하시겠어요?" => What method would you prefer out of regular mail, registered mail, and private service. * 우편 = postal mail. * 등기 = 등기우편 = registered postal mail. * 택배 = by a private delivery service (this may vary widely). I believe both 등기우편 and 택배 automatically provides tracking in both countries. You can answer it like: - 등기로 보내 주세요 = 등기우편으로 보내 주세요 = Please use the registered mail. - (조회 가능한) 등기우편으로 보내 주세요 = Please mail it registered (with tracking) - if you want to emphasize tracking.