某种代码由3位字符组成，每位可选择8种字符，则代码的总数是（）。
A.1000
B.24
C.6561
D.512
参考答案：D
低张型宫缩乏力时首选：
A．吗啡
B．哌替啶
C．小剂量麦角新碱
D．缩宫素静脉点滴
E．苯巴比妥钠
He didn't make________clear when and where the meeting would be held. [ ]
A. this
B. that
C. it
D. these
