In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet. Heterogeneous network environments consist of computer systems from (66) vendors that run (67) operating systems and communication protocols. An organization that (68) its computer resources is usually (69) the task of integrating its heterogeneous systems. Typically, each deparlment or division has defined its own network needs (70) OS, LAN topology, communication protocols, applications, and other components.

A．same

B．similar

C．different

D．difference

普通硅酸盐水泥，代号为（）

A.P·S

B.P·O

C.P·F

D.P·C