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在一定空间范围内同一物种所有个体的集合称为______。

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所有进出我国关境从事商业性国际运输的船舶必须缴纳船舶吨税。( )

A. 对
B. 错

Announcement on Beijing Olympic Volunteer Slogan Solicitation (征集)Ⅰ. Starting and ending dates The open solicitation starts from March 31 and ends on August 31, 2006Ⅱ. Requirements of the slogan1.Highly summarizing the concept of Beijing Olympic Volunteer Program — "service first and harmony first" and highlighting the striking feature of the times and the Chinese culture throughout the Beijing Olympic Games.2. Clearly reflecting the idea that "Volunteers’ smiles are the best name card of Beijing".3. Carrying international flavor and catering to the world so that people from different countries and regions and of various cultural backgrounds can understand and accept it. Both the Chinese version and the English one should be equally impressive.4. Being brief, rhythmic, easy to remember, inspiring and appealing. What does the slogan highlight The striking feature of the times and ______.

Fears of "mad cow" disease spread (1) the globe last week (2) South Africa, New Zealand and Singapore joining most of Britain’ s European Union partners in (3) imports of British beef. In London, steak restaurants were empty follwing the March 20 announcement by scientists that they had found a (4) link between mad cow disease from British beef and its human (5) , Creutzfeldt-Jakob disease(CJD) . Efforts to reassure consumers and governments proved (6) . France, Germany, Italy, Finland and Greece were among countries which announced bans (7) British beef shipments. A committee of EU veterinary experts, meeting in Brussels, (8) new protective measures but said transmission of the disease from cattle to humans was unproven and did not (9) a general ban on British beef exports. Britain’s own main consumer group advised people to (10) beef if they wanted to be absolutely sure of not (11) CJD which destroys the brain and is always (12) . "Could it be worse than AIDS" The stark headline in Friday’s Daily mail newspaper encapsulated the fear and uncertainty (13) Britain. CJD (14) humans in the same way that BSE makes cows mad—by eating away nerve cells in the brain (15) it looks like a spongy Swiss cheese. The disease is incurable. Victims show (16) of dementia and memory loss and usually die (17) six months. Little is known (18) sure about the group of diseases known collectively as spongiform encephalopathies, which explains (19) some eminent scientists are not prepared to (20) a human epidemic of AIDS-like proportions.

A. have recommended
B. has recommended
C. recommended
D. recommending

一些有毒物质在沿食物链传递的过程中，其浓度逐级升高，这种现象称为生物______。