Which of the following is NOT the purpose of America’s central bank

A．Controlling the flow of money in the economy.

B．Overseeing the activities of banks.

C．Producing and distributing bank notes and coins.

D．Contributing to the maintenance of a stable financial system.

SET协议现在还得不到普及，主要是因为

A．SET不够先进

B．SET的实现过程复杂

C．SET的保密性不好

D．SET没有认证环节