在应收款系统中对同一个单位的应收款与应付款可以对冲，预收款也右以用于冲抵应收款。()

Rapid advances in computer and communication technologies have resulted in the (71) merger of these two fields. The lines have bluned among computing, switching, and digital transmission equipment, and the same digital techniques are being used for data, voice, and image transmission. Merging and evolving technologies, coupled with increasing demands for efficient and timely collection, processing, and (72) of information, are leading to the development of (73) that transmit and process all types of data. The ultimate goal of this evolution is something its proponents-some of the most powerful forces in the computing and telecommunications industries-call the (74) .The (74) will be a worldwide public telecommunications network that will deliver a wide variety of services. The (74) will be defined by the standardization of user interfaces, and will be implemented as a set of digital switches and paths supporting a broad range of traffic types and providing (75) processing services. Inpractice, there will be multiple networks, implemented within national boundaries, but from the user’s point of view there will be a single, uniformly accessible worldwide network.

A．ISDN
B．OSI
C．DDN
D．DSP