255.255.255.255地址称为
A. 有限广播地址
B. 定向广播地址
C. 组播地址
D. 保留地址
有类地址IP地址128.40.21.30的哪一部分表示网络号?
A. 128.40
B. 128
C. 128.40.21
D. 30
What are the most fatal pandemic in recorded history?
A. smallpox
Black Death
C. the 1918 influenza pandemic
D. COVID-19
The World Health Organization (WHO) previously applied a _____stage classification to describe the process by which a novel influenza virus moves from the first few infections in humans through to a pandemic.
A. 4
B. 6
C. 7
D. 5