妊娠期高血压疾病易发生（）
A.前置胎盘
B.胎盘早剥
C.胎膜早破
D.脐带脱垂
E.子宫破裂
参考答案：B
一个圆柱的体积是15立方分米，与它等底等高的圆锥的体积是（ ）。
I had just started back for the house to change my clothes _____I heard my name called. [ ]
A. as
B. for
C. while
D. when
