绒毛膜癌的主要转移途径是
A． * * 检查B．缩宫素静脉滴注C．剖宫产术D．硫酸镁抑制宫缩E．期待疗法
参考答案：C
I used to drink a lot of tea but these days I ＿＿coffee.
A．prefer
B．preferred
C．have preferred
D．am preferring
机械密封摩擦小，功率损耗小，轴和轴套易受磨损。
