34. The designs of the new tools should be ________ carefully, so that we can pick out the one that suits our work.

A．experimented

B．examined

C．exercised

D．tried

TCP/IP协议分为四层，分别为应用层、传输层、网际层和网络接口层。不属于应用层协议的是 (13) ，属于网际层协议的是 (4) 。

A．RPC
B．UDP
C．TCP
D．IP