21. In recent years global warming is becoming concern for people all over the world.A. t

发布时间：2020-08-15 02:15:39


21. In recent years      global warming is being     concern for people all over the world.
A. the; the
B. /; a
C. /; /
D. the; /

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A. the; the
(答案→)B. /; a
C. /; /
D. the; /
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