以下哪项是主动脉瓣关闭不全所致().
A.SAM现象
B.弓背样改变
C.钻石样改变
D.吊床样改变
E.二尖瓣前叶高频震颤
参考答案:E
Not knowing his address , she had some difficulty ________ his house.
A.finding
B.to find
C.found
D.find
体积相等的铜块和铝块,______块的质量大;质量相等的铜块和铝块,______块的体积大.