CDMA系统的信道容量是FDMA系统的（）倍，是TDMA系统的（）倍。
参考答案：20；4
空气进入制氧装置，被分离成氧和氮。
Students don't go to school _____ Saturdays. They do their homework _____ home. [ ]
A. in; at
B. on; at
C. in; for
D. on; from
