Radioactivity occurs naturally. The main source comes from natural sources in space, rocks, soil water and even the human body itself. This is called background radiation and levels vary from place to place, though the average dose is fairly constant. The radiation which is of most concern is artificial radiation which results from human activities. Sources of this include the medical use of radioactive materials, fallout and contamination from nuclear bomb tests, discharges from the nuclear industry, and the storage and dumping of radioactive waste.
While artificial radiation accounts for a small proportion of the total, its effects can be disproportionate. Some of the radioactive materials discharged by human activity are not found in nature, such as plutonium (钚) while others which are found naturally may be discharged in different physical and chemical forms, allowing them to spread more readily into the environment, or perhaps accumulate in the food-chain.<
| In colonial days, huge flocks of snowy
egrets inhabited coastal wetlands and marshes of the southeastern United States.
In the 1800s, when fashion dictated fancy hats adorned with feathers, egrets and
other birds were hunted for their plumage. By the late 1800s, egrets were almost
extinct. In 1886 the newly formed Audubon Society began a press campaign to
shame feather wearers and end the terrible folly. The campaign caught on, and
gradually, attitudes changed and new laws followed. Florida and Texas were the first states to pass laws protecting such birds. Then, in 1900, the United States Congress passed the Lacey Act, forbidding interstate commerce to deal in illegally killed wildlife, making it more difficult for hunters to sell their kill. Since then, numerous wildlife refuges have been established to protect the birds’ feeding habitats. A. (A) To argue that government officials need more information when making laws. B. (B) To identify which animals need to be protected and which do not. C. (C) To suggest that legal terminology continues to change over time. D. (D) To provide the legal definitions of species that are protected by the law. [判断题]业扩配套电网项目工程投资界面标准中,对于新建住宅小区10千伏分界点电源供电设施由公司投资建设，负荷侧受电设施由政府投资建设
A.正确 B.错误 [单选题]犬咬伤后应立即用浓肥皂水或清水冲洗伤口至少（）min，同时用挤压法自上而下将残留伤口内唾液挤出，然后再用碘酒涂搽伤口。
A.5 B.10 C.15 D.20 [简答题]简述腰上三角境界和临床意义。
[单选题]（ ）是指持票人在票据到期日前，将票据权利背书转让给金融机构，由其扣除一定利息后，将约定金额支付给持票人的票据行为。
A.贴现 B.转贴现 C.再贴现 D.回购 [判断题]在同一档距内，架空线最大应力出现在该档高悬点处。
A.正确 B.错误 [多选题]互联电网500kV联络线停送电操作，应考虑的内容包括(____)。
A. 电压和潮流转移，非停电线路不能过负荷 B. 防止线路末端电压超过允许值 C. 线路输送功率不超过稳定限额 D. 防止发电机自励磁 [单选题]下列哪项不是巴比妥类急性中毒的临床表现？( )
A.体温升高 B.昏迷 C.血压降低 D.呼吸抑制 E.休克 [单选题] 工作票签发人应由熟悉人员技术水平、熟悉设备情况、熟悉本规程,并具有相关工作经验的生产领导人、技术人员或经本企业主管生产的副厂长(或总工程师)( )的人员担任。
A.认可 B.同意 C.批准 [单选题] 利用水泵接合器向室内管网供水时,应首先注意( )(中)
A.水泵接合器使用范围 B.水泵接合器耐压能力 C.水泵接合器的接口形式 D.水泵接合器的接口口径 [单项选择]
The world’s population keeps growing. There are now about 4 billion of us on earth. That could reach 6 billion by the end of the century and 11 billion in a further 75 years. Experts have long been concerned about such a growth. Where will we find the food, water, jobs, houses, schools and medicine to care for all these people [多选题]高层建筑应设独立的机械加压送风设施的部位( )。
A.具备自然排烟的防烟楼梯间 B.封闭避难层 C.消防电梯的前室或合用前室 D.封闭避难间 [判断题]417、可以利用屋面砖混砌筑结构、烟囱、通气孔、避雷线等结构作为挂点装置
A.正确 B.错误 [单选题]营运资本投资等于（）。
A.季节性负债数量 B.季节性资产数量 C.季节性资产数量和季节性负债数量的总和 D.季节性资产数量超出季节性负债数量的部分 [判断题]未装自动重合闸装置或重合闸装置未动作的架空线路馈线断路器及线路柱上断路器跳闸后，若未接到异常报告，可强送一次。（ ）
A.正确 B.错误 [判断题]施工现场用电与一般工业或居民生活用电相比具有临时性、流动性和危险性。
A.正确 B.错误 [判断题] 班组长应具备适应变化的能力。
A.正确 B.错误 [单项选择]下列不属于股骨头缺血坏死典型X线表现的是
A. 股骨头斑片状密度增高 B. 股骨头限局性疏松、囊变 C. 股骨头不均匀硬化 D. 股骨头塌陷 E. 关节间隙变窄 [单选题]()的分子间隙最小。
A.液体； B.气体； C.固体； [判断题]为了达到帕累托最优，必须使任何只消费两种商品的消费者所消费的这两种产品之间的边际替代率相等。
[判断题] DK-1型电空制动机的特点是：减压量准确，充风快和排风快，手柄操作轻快，司机室噪声小，结构简单以及具有多重性的安全措施。（）
A.正确 B.错误 我来回答: 提交
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