对进行性肌营养不良症采取的主要预防措施有（）
A.加强营养
B.加强锻炼
C.使用肌生注射液
D.检出携带者
E.产前诊断
参考答案：D, E
— They say Tom's brother is a billionaire.
— ________? He wouldn't accept any help from his brother, even though it was offered. [ ]
A. What if
B. What for
C. So what
D. Forget it
诊断最常用的超声频率是
A．20Hz以上
B．20MHz以上
C．20KHz-20MHz
D．2-10MHz
E．1kMHz以下
