外汇行情exchange quotation现汇汇率spot rate即期汇票sight bill汇票议付negotiation of draft票据背书endorse a bill货到付现款cash on arrival凭票据付现款cash against documents凭提单付现款cash against bills of lading承兑交单documents against acceptance(D\A)付款交单documents against payment(D\P)信用证letter of credit(L\C)不可撤消信用证irrevocable L\C保兑信用证confirmed L\C可转让信用证transferable L\C无追索权信用证without recourse L\C开出信用证issue a credit取消信用证cancel a credit修改信用证amend a credit