Analysis of test questions: the point of view of option A is inconsistent with the meaning of the question. In the question, the bank credit card and the payment voucher of current deposit are not the same thing. The payment voucher of demand deposit is a deposit voucher, so it is excluded. The point of view of option b is inconsistent with the meaning of the question. Bank credit cards are not commodities and have no value, so they are excluded. Option c is inconsistent with the meaning of the question. The bank credit card itself has no value and cannot perform the function of value scale, so it is excluded. The point of view of option d is inconsistent with the meaning of the question. Bank credit cards are used for consumption, not loans, so they are excluded.