不与钙离子结合的抗凝剂是 （） A.枸橼酸钠 B.EDTA－Na2 C.EDTA－

Fear seems to be the dominant mood of the moment. Hurricanes, tidal waves, floods, earthquakes and terrorism this year have all brought with them not only appalling scenes of devastation, death and suffering, but also outrage at the lack of preparations to avoid or cope with these disasters. Now even the birds of the air are a threat, we are told. That migrating flock visible On the horizon at sunset, once a consoling reminder of the eternal rhythms of nature, could be carrying the virus which might soon kill tens of millions of people.

Given the many fingers pointed at governments in the wake of other disasters this year, it is hardly surprising that they are scrambling to respond to the threat posed by avian influenza. After confirmation this week that the HSN1 strain of bird flu, which has been spreading quickly in Asia, had been discovered in Romania and perhaps Greece, European Union foreign ministers convened an emergency meeting. President George Bush, still smarting from a torrent of criticism of his government’s clumsy response to Hurricane Katrina, has promised to rush out emergency plans for dealing with an outbreak of pandemic flu which have been stalled for years. Countries around the world are hurrying to stockpile the only current antiviral drug, Tamifln, which might be effective in saving lives in any pandemic or curbing its spread. The World Health Organisation is calling for an internationally coordinated effort. Health ministers from around the globe are due to meet next week in Canada to discuss what steps to take.

Is any of this eff6rt justified Or are politicians simply helping to feed public panic, and then covering themselves by promising to spend lavishly against a threat which may never materialize and to reduce a risk which they do not understand To ask these questions is not to counsel complacency, but to apply the kind of test which is required in any kind of disaster planning, not least because the world is an inherently dangerous place and it is impossible to plan against every possible disaster. With the media full of warnings of impending mass death, an overreaction is all too possible.

According to the text, American emergency plans for coping with an outbreak of pandemic flu （）

A. have been stipulated

B. have been enacted

C. have been abolished

D. have been delayed

体力活动可使其发生的危险性减少的是（）

A.胃癌

B.肝癌

C.鼻咽癌

D.乳腺癌

E.结肠癌

请你写出一个含字母x，并且当x≤2时在实数范围内有意义的二次根式（    ）。

分馏的仪器装置安装和拆卸的原则是什么？

闪光警告信号灯为持续闪烁的黄灯，它的作用什么？