牙周基础治疗后牙龈增生仍明显采取的术式是（）
A.引导性组织再生术十植骨术
B.牙冠延长术
C.根向复位瓣术
D.截根术
E.牙龈切除术
参考答案：E
pH为1.0和3.0的两种强酸的水溶液等体积混合后，溶液的pH为（）。
A．1.0
B．1.5
C．2.0
D．1.3
Our hometown is more beautiful than before, ______?[ ]
A. isn't it
B. is it
C. doesn't it
D. does it
