下面成语不能帮助我们了解春秋时期诸侯争霸历史的是 [ ]
A．反戈一击
B．退避三舍
C．一鸣惊人
D．问鼎中原
答案：A
He is a student at Oxford University, ____for a degree in computer science.
A．studied
B．studying
C．to have studied
D．to be studying
在下列给出的协议中，（）是TCP/IP的应用层协议。
A.TCP
B.ARP
C.FTP
D.DNS
