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问题 选择题

如图所示为两个带等量点电荷周围的电场线分布（电场线方向未标出），则  

A．A只能带正电

B．A只能带负电

C．若A带正电，则 B肯定是带负电的

D．若A带正电，则B肯定是带正电的

答案

答案：C

根据等量异种电荷电场分布可得，AB为异种电荷，所以若A带正电，则B肯定是带负电的，C正确。

单项选择题

在Ca2+、Mg2+的混合溶液中用EDTA法测定Ca2+时，消除Mg2+的干扰宜用（）

A.控制酸度法

B.沉淀掩蔽法

C.氧化还原掩蔽法

D.络合掩蔽法
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单项选择题

Lobbying groups often try to disguise a financial self-interest by clumsily dressing up their arguments in the guise of concern for the public. You see this tendency in the pharmaceutical industry (21) in energy and lumber companies who like to tout their (22) of the environment. But (23) , two new books argue, are these tactics more (24) a cause for concern than in agribusiness.
Marion Nestle’s "Food Safety: Bacteria, Biotechnology, and Bio-terrorism’ looks at the way the American meat and biotechnology industries have (25) successfully on Capitol Hill (26) stricter federal regulation, which the author argues has undermined the safety of the food supply.
(27) , Maxime Schwartz’s "How the Cows Turned Mad" (28) the origins of mad-cow disease over more than two centuries, and reveals the fallout from the British government’s blind (29) that the disease could not be (30) to humans.
In 1999, Ms Nestle writes in her earlier book, Rosemary Mueklow, the executive director of the National Meat Association, lobbied against President Clinton’s (31) to establish a more thorough testing regime for E. coli 0157: H7, a potentially (32) pathogen.
Ms Muck low’s organization—which represents meatpackers and processors who (33) to discard or reprocess meat found to be infected under the new testing regime—argued on Capitol Hill that (34) microbial testing in meat could actually lead to a greater public health risk (35) confident consumers might relax their own safe-handling procedures at home.

A. transformedB. transmittedC. transportedD. infected
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