会计科目代码结构是指代码共有多少个以及各级代码的长度。 ( )

Microsoft’s COM is a software architecture that allows applications to be built from binary software components. COM is the underlying (48) that forms the foundation for higher-level software services, like those provided by OLE. COM defines a binary standard for function calling between components, a way for components to dynamically discover the interfaces implemented by other components, and a mechanism to identify components and their interfaces uniquely.

OLE is a compound (49) standard developed by Microsoft. OLE makes it possible to create (50) with one application and link or embed them in a second application. Embedded objects retain their original format and (51) to the application that created them. Support for OLE is built into the Windows and MacOS Operating Systems. A (52) compound document standard developed mainly by Apple and IBM is called OpenDoc.

48（）

A.architecture 

B.structure 

C.procedure 

D.protocol