关于履约担保的说法，正确的有（）。 A.建筑业通常倾向于采用无条件银行担保函作为履约

著明物理学家李政道说：“科学与艺术是一个硬币的两面。为了心情愉快，松弛一下紧张的工作，我有时间就喜欢画画，听听音乐，读读文学。”这说明（　　 ）

A．研究科学就是研究艺术，两者没有区别

B．科学家的生活都很单调，缺乏高雅情趣

C．高雅的生活情趣有益于个人的身心健康

D．只有科学家才培养自己高雅的生活情趣

（10分）【自然灾害与防治】

下图为某地区多年平均气温和降水变化示意图。读图回答下列问题。

（1）说出当地近年来干旱多发的原因。(6分)

（2）例举干旱造成的危害。(4分)

阿伏加德罗常数给出物质的量的“标准1”，即1 mol具体代表多少粒子。显然粒子数与物质的量成比例。 已知amolH₂SO₄中含有b个氧原子，则阿伏加德罗常数可以表示为[ ]

A.

B.

C.

D.

下列关于突发事件处置应对工作，做法错误的是（）。

A.甲市乙县发生突发事件，乙县人民政府立即采取应对处置措施，并向甲市人民政府报告

B.丙市人民政府成立由市长以及公安、安监、卫生等相关部门负责人，驻当地中国人民解放军和中国人民武装警察部队有关负责人组成的突发事件应急指挥机构

C.丁市发生突发事件后，市公安局组织突发事件应急机构相关部门，开展救援处置工作

D.戊县发生出租车司机大规模非法占道事件后，该县公安局迅速出警，采取交通管制措施恢复交通秩序

British cancer’ researchers have found that childhood leukaemia is caused by an infection and clusters of cases around industrial sites are the result of population mixing that increases exposure. The research published in the British Journal of Cancer backs up a 1988 theory that some as yet unidentified infection caused leukaemia--not the environmental factors widely blamed for the disease.

"Childhood leukaemia appears to be an unusual result of a common infection," said Sir Richard Doll, an internationally-known cancer expert who first linked tobacco with lung cancer in 1950. "A virus is the most likely explanation. You would get an increased risk of it if you Suddenly put a lot of people from large towns in a rural area, where you might have people who had not been exposed to the infection. " Doll was commenting on the new findings by researchers at Newcastle University, which focused on a cluster of leukaemia cases around the Sellafield nuclear reprocessing plant in Cumbria in northern England. Scientists have been trying to establish why there was more leukaemia in children around the Sellafield area, but have failed to establish a link with radiation or pollution. The Newcastle University research by Heather Dickinson and Louise Parker showed the cluster of cases could have been predicted because of the amount of population mixing going on in the area, as large numbers of construction workers and nuclear staff moved into a rural setting. "Our study shows that population mixing can account for the (Sellafield) leukaemia cluster and that all children, whether their parents are incomers or locals, are at a higher risk if they are born in an area of high population mixing," Dickinson said in a statement issued by the Cancer Research Campaign, which publishes the British Journal of Cancer.

Their paper adds crucial weight to the 1988 theory put forward by Leo Kinlen, a cancer epidemiologist at Oxford University, who said that exposure to a common unidentified infection through population mixing resulted in the disease.

This passage is mainly about（）

A. the cluster of leukaemia cases around the Sellafield nuclear reprocessing part

B. the kind of infection that causes childhood leukaemia

C. the causes of childhood leukaemia

D. a new finding by British scientists