53.有關信用狀提單之規定，下列何者應經由託運人（shipper）背書始能流通轉讓，否則持有人不能辦理提貨手續？ (A) B/L made out to order of negotiating bank… (B) B/L made out to order of shipper and blank endorsed… (C) B/L made out to order of issuing bank… (D) B/L consigned to order of buyer…