TCP/IP（请作答此空）layer protocols provide services to the application（ ）running on a computer.The application layer does not define the application itself,but rather it defines（ ）that applications need--like the ability to transfer a file in the case of HTTP.In short,the application layer provides an（ ）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（ ）layer consists of two main protocol options--the Transmission Control Protocol（TCP）and the User Datagram Protocol（UDP）.
选项：

A:application
B:transport
C:link
D:network