The key the earth is to change the way we live.
A. to save; /
B. to saving; /
C. to save; how
D. to saving; how
网友回答
A. to save; /
(答案→)B. to saving; /
C. to save; how
D. to saving; how
解析：本题考查名词及定语从句。The key to doing sth.做某事的关键，to为介词；定语从句the way为先行词，关系词为that/in which/\，选B。