Documentary credits are separate transactions from the sales contract with which they are related and Letter of Credit can be divided into many kinds depending on the circumstance. A documentary credit may be available by payment, by negotiation or by acceptance. (1) means that the nominated bank will pay the beneficiary the full amount due once he submits the contract documents required under the credit. Under a (2) , the beneficiary is given double assurance of payment since the confirming bank has added its own undertaking to that of the opening bank. If a credit can be transferred by the original beneficiary to one or more parties, it is a (3) . If a credit stipulated that its amount can be renewed without specific amendment to the credit being made, it is then a (4) . (5) are those that cannot be amended or revoked without the consent of all the parties concerned. 4（）

A. sight credit
B. transferable credit
C. revolving credit
D. back-to-back credit