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问题 单项选择题

下列关于我国节约能源法律制度的说法中，正确的是（）。

A.节约能源是我国的基本国策

B.国家鼓励电力用户合理调整用电负荷，对钢铁、有色金属、建材和化工行业企业，禁止实行差别电价

C.企业不得制定严于国家标准、行业标准的节能标准

D.国家对节能产品认证实行强制原则

答案

参考答案：A

单项选择题

The most popular organic gem is the pearl. A pearl is the response of a marine mollusk to the presence of an irritating impurity accidentally introduced into its body; a cultured pearl is the result of the intentional insertion of a mother-of-pearl bead into a live mollusk. Whether introduced accidentally or intentionally, the pearl-making process is the same: the mollusk coats the irritant with a substance called nacre. Nacre is composed chiefly of calcium carbonate. Because very few natural pearls are now on the market, most pearls used in fine jewelry are cultured. These include "Biwa" pearls and most other freshwater pearls. Cultured pearls are not easily distinguished from natural pearls except by an expert.

The main idea in this passage is that________.

A．most marketable pearls are cultured because nature does not produce enough of its own to satisfy the market

B．cultured pearls are of a higher quality than natural pearls

C．there are two major methods of pearl-making

D．a natural "drought" of pearl production is taking place
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单项选择题

泪液分泌试验低分泌为低于（）

A.5min10mm

B.5min8mm

C.5min5mm

D.3min8mm

E.8min10mm
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