90% of the credit amount must be paid ______ the presentation of

90% of the credit amount must be paid ______ the presentation of documents.
A、at
B、by
C、against
D、with
【正确答案】：C
【题目解析】：[解析]句意：根据提交的文件，必须支付90%的总信用额。against表示“以为标准，根据”，符合 题意。