The use of the battery-powered devices known as e-cigarettes may lessen smoking rates, but until it has been demonstrated neither to have adverse side effects nor to increase tobacco addiction, it should not be recommended as a substitute for tobacco cigarettes.
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Auntil it has been demonstrated neither to have adverse side effects nor to increase tobacco addiction, it should not be recommended
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Bit should not be recommended before it has been demonstrated not to have adverse side effects or increase addiction
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Cdemonstrating that it does not have adverse side effects or increase addiction, it would not be recommended
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Dwithout adverse side effects or increased addiction demonstrated, it should not be recommended
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Ewithout a demonstrated lack of side effects or increased addiction, it would not be recommended
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显示答案
正确答案: A