以下属于2G系统的是（）。
A.IS-95
B.CDMA2000
C.GSM
D.PHS
参考答案：A, C, D
— What's your father doing now?
— He ______ the room [ ]
A. cleaned
B. cleans
C. has cleaned
D. is cleaning
社会主义市场经济有哪些基本特征
