6. Measures have been taken to prevent a
问题:
6. 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
6. 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