25 ．具有双重保证的信用证是（　　　）

A ．可转让信用证                                             B ．对开信用证

C ．可撤销信用证                                             D ．保兑信用证

26 ．按一般惯例，合同的罚金数额不宜超过货物总金额的（　　　）

A ． 3 ％                                                             B ． 5 ％

C ． 8 ％                                                             D ． 10 ％

27 ．信用证开立的依据是（　　　）

A ．汇票                                                           B ．本票

C ．发票                                                           D ．买卖合同

28 ．减价拍卖又叫（　　　）

A ．英国式拍卖                                                 B ．荷兰式拍卖

C ．淘汰式拍卖                                                 D