问题
选择题
There is still a long way to go to work out all the problems ________ conservation of natural resources. [ ]
A. concerning
B. concerned
C. to concern
D. concern
答案
答案：A
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There is still a long way to go to work out all the problems ________ conservation of natural resources. [ ]
A. concerning
B. concerned
C. to concern
D. concern
答案：A