6. Because unvented gas fireplaces exhaust directly into the room rather than outside, they also emit pollutants which may _____ some health risks.
(A) run
(B)vent
(C) entail
(D) include
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統計: A(3), B(5), C(32), D(3), E(0) #814334
統計: A(3), B(5), C(32), D(3), E(0) #814334