胎盘早剥常见于下列哪项妊娠并发症（）
A.妊娠期高血压疾病
B.甲亢
C.糖尿病
D.心脏病
E.贫血
参考答案：A
Statistics show that men have _____ as women do for every mile they drive．
A．serious accidents as twice many
B．twice as many serious accidents
C．twice serious accidents as many
D．serious accidents as many twice
试验研究中对照组与实验组发病率之比，为
A．有效率B．治愈率C．生存率D．保护率E．效果指数
