问题
＿＿＿＿＿ is our duty ＿＿＿＿＿ the environment.
A:This; protect
B:It; to protect
C:This; protecting
D:It; protect;
B:It; to protect
C:This; protecting
D:It; protect;
正确答案是：
同类题型
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