问题
选择题
21. In recent years _____ global warming is becoming ____concern for people all over the world.
A．the; the
B．/; a
C．/; /
D．the; /
答案
答案：B
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21. In recent years _____ global warming is becoming ____concern for people all over the world.
A．the; the
B．/; a
C．/; /
D．the; /
答案：B