肉毒素在整形美容中使用出现的并发症中哪项不正确（）
A.永久性神经损害
B.面部表情呆滞
C.张口功能受限
D.上睑下垂
E.听力下降
参考答案：E
They are said () each other long time before they met in Harvard University where they worked together on a research project.
A. to know
B. to have known
C. knowing
D. having known
什么叫操作过电压？主要有哪些？
