Measures have been taken to prevent accidents but much for more improvement.A. remains t

问题补充：

Measures have been taken to prevent accidents, but much for more improvement.

A. remains to be done

B. is remained to do

C. remains to do

D. is remained to be done

答案：

(答案→)A. remains to be done

B. is remained to do

C. remains to do

D. is remained to be done

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