习惯性晚期流产最常见的原因是
A.孕卵发育异常
B.黄体功能不全
C.甲状腺功能不全
D.胎膜破裂
E.子宫颈内口松弛
参考答案:E
Please be quiet. We are not allowed _______ much noise in the reading room. [ ]
A. to make
B. make
C. making
D. to making
空气的加湿方法一般有( )。
A.喷水加湿
B.喷蒸汽加湿
C.超声波加湿
D.近红外线加湿