TCP/IP （） 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).

（）running on a computer.

A．hardware

B．software

C．packet

D．equipment

在下面有关光合作用的叙述中，正确的是（）

A.光反应不需要酶，暗反应需要多种酶

B.光反应消耗ATP，暗反应形成ATP

C.光反应固定二氧化碳，暗反应还原二氧化碳

D.光反应消耗水，暗反应消耗ATP