31 The flood warning system needs to be______ established to save thousands of lives.
(A) minimally
(B) optimally
(C) improperly
(D) optionally
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統計: A(27), B(126), C(118), D(47), E(0) #3256037
統計: A(27), B(126), C(118), D(47), E(0) #3256037