目前，( )是我国政府特别是中央政府财政收入最主要的来源，其收入居各税之首，约占我

—Did you read the book Who Stole My Cheese ?

—Yes. I___________it twice while in university.

A．reads

B．read

C．had read

D．has read

某投资者用300万元购买了一商铺20年的经营权，当年出租，每年年末净租金收入为40万元，投资者的目标收益率为10%，银行贷款年利率为7%，该项投资的财务净现值是（）万元。

A.40.54

B.123.76

C.268.50

D.500.00

传统渠道系统结构简单，管理方便。（）

高压设备发生接地时，室内不得接近故障点8m以内。

Frame Relay is simplified form of (71) ,similar in principle to (72) , in which synchronous, frames of data are routed to different destinations depending on header information. Packets are routed throught one or more Virtual Circuits known as (73) . Most Virtual Circuits are (74) ,which means that the network provider sets up all DLCI connections at subscription time. (75) are also part of the Frame Relay specification. They privide a link that only lasts only as long as the session.

A．Datagram Switching

B．Datagram Routing

C．Packet Switching

D．Packet Routing