虽无临床症状但要不断排除病原体，称为（）。
A.不感染
B.潜伏感染
C.慢性病毒感染
D.隐形感染
E.病原携带状态
参考答案：E
电信网按服务对象分，有（）。
A.公用通信网
B.数字通信网
C.数据通信网
D.专用通信网
One of the most inportant questions they had to consider was ____ of public health. [ ]
A. that
B. this
C. that
D. which
