关于酸蚀症,正确的是
A.多见于喜食酸性食物者
B.仅有牙本质感觉过敏症状
C.由于酸雾或酸酐作用于牙齿而造成
D.无牙体实质缺损
E.可引起楔状缺损
参考答案:C
—Is the boy your own son?
—No. He is an _____ child _____ himself Martin.
A.adopted, calling
B.adopted, called
C.adopting, calling
D.adopting, called
为提高CNC系统的可靠性,可采用_____。
A.单片机
B.双CPU
C.提高时钟频率
D.光电隔离电路