第一阶段的计算机网络系统实质是（）
A.APRA网
B.资源共享的计算机网络
C.面向终端的计算机通信网络
D.计算机与计算机之间的通信网络
参考答案：C
While these different forms of greetings and customs might seem strange to you, remember ________ you consider normal probably seems equally strange to others.[ ]
A. that
B. what
C. which
D. when
直升机的旋翼类型分为哪几种，非对称双凸型有什么优缺点？
