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问题 选择题

蛔虫生活在人的消化道内，长期得不到氧气，因此它的细胞内的哪种结构可能消失（　　）

A．细胞膜

B．细胞核

C．线粒体

D．细胞质

答案

A、细胞膜的作用是控制物质的进出有用的物质不能轻易渗出，有害的物质不能轻易的进入．故不符合题意．

B、细胞核内含有遗传物质，是遗传控制的中心．故不符合题意．

C、线粒体想呼吸作用的场所，能将细胞中的有机物在氧的参与下分解为二氧化碳和水，同时将有机物中的化学能释放出来，供细胞利用．结合题意可知，蛔虫生活在人的消化道内，长期得不到氧气，因此它的细胞内的线粒体可能消失．符合题意．

D、细胞质具有流动性，能加速细胞内外物质的交换．不符合题意．

故选：C

单项选择题

某商业银行在95%置信区间、1天持有期的条件下，报告期内交易账户风险价值为660万元人民币，假设其他条件不变，如果置信区间提高至99%，则该银行交易账户的风险价值将（）。

A.保持不变

B.减小

C.无法判断

D.增加
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单项选择题

Even plants can run a fever, especially when they are under attack by insects or disease. But (1) humans, plants can have their temperature (2) from 3,000 feet away—straight up. A decade ago, (3) the infrared scanning technology developed for military purpose and other satellites, physicist Stephen Paley (4) a quick way to take the temperature of crops to determine (5) ones are under stress. The goal was to let farmer (6) target pesticide spraying (7) rain poison on a whole field, which (8) include plants that don’t have the pest problem.

Even better, Paley’s Remote Scanning Services Company could detect crop problem before they became (9) to the eye. Mounted on a plane flown at 3,000 feet (10) , an infrared scanner measured the heat emitted by crops. The data were (11) into a color-coded map showing (12) plants were running "fevers". Farmers could then spot spray, using 50 to 70 percent less pesticide than they (13) would.

The bad news is that Paley’s company closed down in 1984, after only three years. Farmers (14) the new technology and long-term backers were hard (15) . But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to (16) into operation. Agriculture experts have no doubt about the technology works. "This technique can be used (17) 75 percent of agricultural land in the United States," says George Oerther of Texas A＆M. Ray Jackson, who recently retired from the Department of Agriculture, thinks (18) infrared crop scanning could be adopted by the end of the decade. But (19) Paley finds the financial backing (20) he failed to obtain 10 years ago.

12（）

A.how

B.where

C.what

D.when
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