．Many in the credit industry expect that credit cards will eventually ________ paper money for almost every purchase.

A.exchange   B.decrease                   C. trade                          D replace

采用碘量法测定烟气中光气时，如有氯气存在会影响测定，可在吸收瓶前串联一个装有碳酸钠的U形吸湿管，以排除氯气的干扰。