What do we learn about the untreated industrial chemical wastes from the passage?
A.They can conserve the normal biological action of rivers.
B.They all react with water to increase the acidity of rivers.
C.They make the water corrosive enough to destroy living organisms.
D.There are no rules for concentrations of unquestionably toxic chemicals of drinking water.
第7题
奶类及其制品的主要卫生问题是:腐朽变质,人畜共患传染病和致病菌(金黄色葡萄求菌等)农药及抗生素残留,重金属及放射性物质污染,霉菌毒素污染及掺假掺杂等。()
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