高危妊娠
参考答案：高危妊娠 指妊娠期有个人或社会不良因素及有某种并发症或合并症等可能危害孕妇、胎儿或者导致难产者。
二尖瓣区收缩期器质性杂音的听诊特点不包括（）
A.高调
B.性质粗糙
C.吸气时增强
D.向左腋下传导
E.吹风样
It be difficult to get a train ticket during traditional Chinese Spring Festival this year because there are
many ticket windows. [ ]
A. mustn't
B. ought to
C. needn't
D. can't
