支持Internet扩展服务协议是：（）
A.OSI
B.IPX／SPX
C.ICP／IP
D.CSMA／CD
参考答案：C
. This tower _______ back to 1860s and it is still in good condition.
A．is dating
B．dated
C．was dated
D．dates
中正还要注意哪些？
