TCP/IP (1) layer protocols provide services to the application (2) running on a computer. The application layer does not define the application itself, but rather it defines (3) that applications need — like the ability to transfer a file in the case of HTTE In short, the application layer provides an (4) between software running on a computer and the network itself. The TCP/IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP/IP (5) layer consists of two main protocol options — the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

4（）

A.iteration 
B.object 
C.interface 
D.activity