哪项特征描述的是 IPv6 相比于 IPv4 的增强功能？
A. IPv4 和 IPv6 都支持身份验证，但只有 IPv6 支持隐私保护功能。
B. IPv6 地址基于 128 位平面编址，而 IPv4 基于 32 位分层编址。
C. IPv6 报头比 IPv4 报头简单，增强了数据包处理。
D. IPv6 的地址空间比 IPv4 的地址空间大四倍。
查看答案
将命令与输入命令时所处的设备模式配对。 （并非所有选项都会用到）。
Section CDirections: In this section, you will hear three passages. At the end of each passage, you will hear three or four questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D). Then mark the corresponding letter on Answer Sheet 1 with a single line through the centre.[音频]Question16
A. The importance of sleep to a healthy life.
B. Reasons for Americans' decline in sleep.
C. Some tips to improve the quality of sleep.
Diseases associated with lack of sleep.
Question17
A. They are more health-conscious.
B. They are changing their living habits.
C. They get less and less sleep.
D. They know the dangers of lack of sleep.
Question18
A. Their weight will go down.
B. Their mind function will deteriorate.
C. Their work efficiency will decrease.
D. Their blood pressure will rise.
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