血站是采集、提供临床用血的机构，是不以营利为目的的公益性组织。（）

Когда директор вошел в кабинет, в руке у него было письмо, ____ утром.

A． полученное

B． получившее

C． получено

D．получаемое

能导致爆炸的粉尘，首推金属粉尘，特别是（）。

A.铜粉

B.铁粉

C.铅粉

D.铝粉

花瓷

甲房地产开发公司(以下简称甲公司)获得一居住用地的开发权，经过市场调研后拟定了两个开发方案：方案一为投入2亿元开发高档住宅，建筑面积80000m²；方案二为投入1.8亿元开发普通住宅，建筑面积100000m²。甲公司对销售前景进行了预测：高档住宅销路好的概率为60%，可获收益5000万元；销路差的概率为40%，将会亏损3000万元。普通住宅销路好的概率为80%，可获收益3000万元；销路差的概率为20%，将会亏损1000万元。

对普通住宅开发的投资风险有影响的因素主要有( )。

A．销售价格

B．住房政策

C．位置与环境

D．客户状况

A few milliamps of electricity can cause plants to increase synthesis of chemicals. These compounds often also have a pharmacological (related to medicine) or commercial value, so the trick could be used to help increase yields of commercially useful biologicals. Artemisinic acid, from sweet wormwood, for example, is used in malarial medications, and shikonin (紫草素), from the purple gromwell plant, is used against skin infections.

Researchers have long known that stressing plants can force them to take defensive action, often ramping up the production of protective chemicals that, for example, make them more resistant to insect attack. It has become common practice to stress such plants into increasing their yields. This is usually clone using physical stress elicitors (诱导子), including bits of the micro-organisms that normally attack the plants, or irritants made from metallic compounds such as copper chloride. These are effective, but they come at a cost. Most elicitors are toxic to plants and can build up in tissues, making it necessary to occasionally "clean" a plant of the chemicals so they keep having the same effect.

Recently, research groups at the University of Arizona in Tucson found that the application of an electric current to the hairy roots of the poisonous herb Hyoscyamus muticus stimulated the production of the herb’s toxin hyoscyamine (天仙子胺). This unpublished finding inspired Hans Van Etten, also of the University of Arizona, and his colleagues to test sub-lethal levels of electrical currents on other plants, to assess electricity’s potential to elevate chemical production.

The researchers exposed eight different plant species (ranging from Japanese pagoda tree seedlings to pea plants) to weak electrical currents of 30 milliamps. Seven of the plants increased their production o defensive chemicals. The average boost of chemical production was 20 times, they report in Biotechnology Progress. One plant, a type of alfalfa, increased its chemical yield by 168 times. These values are very similar to those achieved using chemical elicitors, and seem to have no lethal effects-just a negative effect on growth. The treatment can be used over and over again without the build-up of any unwanted material.

The useful compounds would be very easy to harvest: they simply pour out into solution if the plants are grown hydroponically. "The fact that we can use electricity instead of toxic materials to elicit chemical production is very exciting because it means we get to look at how these chemicals form without having to constantly add and remove toxins from the system," says Van Etten. "This is a really novel and creative approach that I’ve never seen before," says plant metabolic engineer Fabricio Medina Bolivar from Arkansas State University in Jonesboro. "The possibilities for using electricity with plants in this way are absolutely tremendous.

Which one of the followings is NOT the advantage of using electricity（）

A. It can achieve the same values as using chemical elicitors

B. It can be used time and again

C. It can boost chemical production

D. It has no adverse impacts on the growth of plants