Everyone here will thank the firefighters for the things they have done to prevent fires the environment safer.
A. make
B. to making
C. to make
D. from making
网友回答
A. make
B. to making
(答案→)C. to make
D. from making
解析：从语法角度考虑可排除A、B两项，D项符合语法，但句意不妥，C项不定式结构表结果。