问题
选择题
We can never expect _______bluer sky unless we create _______less polluted world. [ ]
A. a; a
B. a; the
C. the; a
D. the; the
答案
答案：A
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We can never expect _______bluer sky unless we create _______less polluted world. [ ]
A. a; a
B. a; the
C. the; a
D. the; the
答案：A
2CO2变化中的最小粒子是