He has made up his mind to devote his life _________ pollution _________ happily.

A．to prevent; to live

B．to prevent; from living

C．to preventing; to live

D．to preventing; from living

固定义齿修复中，若前牙缺隙小于对侧同名牙，可以通过以下措施改善美观，除外（）

A.适当磨除基牙的近缺隙面牙体组织

B.加大桥体唇面突度，扩大邻间隙

C.减小桥体唇面突度

D.制作近远中向横沟、纹

E.排牙时将桥体牙适当扭转或与邻牙重叠