According to the passage, what should be done to potentially harmful substances?
(A)They should be kept carefully.
(B)They should be used randomly.
(C)They should be bought from a store.
(D)They should be dumped.
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統計: A(594), B(106), C(130), D(51), E(0) #339601
統計: A(594), B(106), C(130), D(51), E(0) #339601