深龋备洞无需做到（）
A.间断、慢速磨除
B.尽量保留健康牙体组织
C.底平壁直
D.洞缘线圆钝
E.去尽腐质
参考答案：C
People are strongly advised _____ legal means to settle their disputes. [ ]
A. to take
B. taking
C. take
D. to be taken
一元二次方程x2=1的解为 _________ ．
