— Ready to give up, Jim?

— No, Hold on! I think I _____to the answer. [ ]

A. come

B. am coming

C. came

D. have come

IP城域网存在的安全隐患有（）

A.黑客入侵和网络攻击

B.软件bug

C.网络结构单点隐患

D.设备性能或链路带宽资源不足