将一条物理信道按时间分成若干个时间片轮流分配给多个信号使用的复用技术是（）
A. 频分多路复用（FDM）
B. 时分多路复用（TDM）
C. 码分多址（CDM)
D. PCM
（）是用数字技术对现有的模拟电话用户线进行改造，使它能够承载宽带业务。
A. xDSL
B. HFC
C. FTTx
D. WIFI
城市地理学研究的核心问题是
A. 城市的空间组织演化
B. 城市的发展模式
C. 城市的发展条件
Which of the following sentences has a misplaced modifier?
A. He only talks about changing his working plan. [Intended meaning: He only talks but does nothing else, about changing his working.]
B. A girl appeared in my dreams that sang like an angel.
C. The book on the shelf is hers.
D. All of the above.
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