发现心包积液最简便、准确的方法是（）
A.核素心肌显像
B.超声心动图
C.冠状动脉造影
D.心电图
E.PET
参考答案：B
阻燃剂氢氧化镁[Mg(OH)2]属于
A．氧化物
B．盐
C．碱
D．酸
Mary as well as her sisters ___ Chinese in China. [ ]
A. are studying
B. have studied
C. is studying
