心肌上主要的肾上腺素受体是（）

A．β₁

B．β₂受体

C．M受体

D．N₁受体

E．N₂受体

Microsoft’s COM is a software （66） that allows applications to be built from binary software components. 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 （67）standard developed by Microsoft. OLE makes it possible to create （68）with one application and link or embed them in a second application. Embedded objects retain their original format and （69）to the application that created them. Support for OLE is built into the Windows and MacOS Operating Systems. A （70） compound document standard developed mainly by Apple and IBM is called OpenDoc.

A．characteristics

B．address

C．page

D．links