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问题 单项选择题

在基因工程中，科学家所用的“剪刀”、“针线”和“运载体”分别是指（）

A.大肠杆菌病毒、质粒、DNA连接酶

B.噬菌体、质粒、DNA连接酶

C.DNA限制酶、RNA连接酶、质粒

D.DNA限制酶、DNA连接酶、质粒

答案

参考答案：D

选择题

(2009浙江宁波质检)The building around the corner caught fire last night．The police are now _______ the matter．

A．getting through

B．working out

C．looking into

D．watching over
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单项选择题

It is commonly held among marketing experts that in a nonexpanding market a company’s best strategy is to go after a bigger share of the market and that the best way to do this is to run comparative advertisements that emphasize weaknesses in the products of rivals. In the stagnant market for food oil, soybean-oil and palm-oil producers did wage a two-year battle with comparative advertisements about the deleterious effect on health of each other’s products. These campaigns, however, had little effect on respective market shares; rather, they stopped many people from buying any edible oils at all.
The statements above most ply support the conclusion that comparative advertisements

A．increase a company’s market share in all cases in which that company’s products are clearly superior to the products of rivals.

B．should not be used in a market that is expanding or likely to expand.

C．should under no circumstances be used as a retaliatory measure.

D．carry the risk of causing a contraction of the market at which they are aimed.

E．(E) yield no long-term gains unless consumers can easily verify the claims made.
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