As more and more cars are produced and used, so the _____ from their exhaust-pipes contains an even larger volume of poisonous gas.
A.exposure | B.distribution | C.expansion | D.emission |
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As more and more cars are produced and used, so the _____ from their exhaust-pipes contains an even larger volume of poisonous gas.
A.exposure | B.distribution | C.expansion | D.emission |