塑化治疗技术中的要求是
A．尽量拔除牙髓
B．可以不拔髓
C．必须拔尽牙髓
D．保留根尖1/2处牙髓
E．保留根尖1/3处牙髓
参考答案：A
如果n是方程x2+mx+n=0的根，n≠0，求m+n的值．
A wooden plug fitted tightly in the vent of a damaged tank may prevent the tank from（）.
A.filling completely
B.developing free surface
C.developing free surface moment
D.collapsing
