以下哪个土壤中的金属离子毒害性较小，对人体健康威胁较小（）？

[问答题]Practice 9　　In the United States most people are simultaneously consumers and producers; they are also voters who help influence the decisions of the government. The mixture among consumers, producers and government changes constantly, making a dynamic rather than a static economy. In the last decade consumers have made their concern known and government has responded by creating agencies to protect consumer interests and promote the general public welfare. In another development, the population and the labor force have moved dramatically from farms to cities, from the fields to the factories, and above all to service industries, thus providing more personal and public services. In today's economy these providers of services far outnumber producers of agricultural and manufactured goods.　　Generally, there are three kinds of businesses: (1) those started and managed personally by single owners or single entrepreneurs; (2) the partnership where two or more people share the risks and rewards of a business, and (3) the corporation where shareholders as owners can buy and sell their shares at any time on the open market. This latter structure, by far the most important, permits the amassing of large sums of money by combining investment of many people, making possible large-scale enterprises.

[判断题]从认识论的角度看，教学是教师教学生认识世界的活动。

[单选题]《汉书》是我国第一部断代史，它的编纂体例是（　　）。

[问答题]简述19世纪现实主义的主要特征。

[判断题]推铅球时，铅球应完全落在落地区标志线外沿以内。

[问答题]如何认定使用与知名商品近似的名称、包装、装潢的行为？

[单选题]在审计过程中，下列不属于注册会计师为识别出关联方存在审计程序的是（　）。

[多选题]中性粒细胞成熟障碍包括（）

[单选题]人民法院在裁定设定抵押的被执行人及其所扶养家属居住的房屋拍卖后，应当给予被执行人的宽限期是()个月。

[问答题]新时期基础教育改革对教师专业发展提出什么要求和挑战？

[多选题]重金属离子在土壤中的形态有哪些（）？

[判断题]土壤对重金属离子的吸附能力与金属离子的性质及胶体种类有关。

[判断题]土壤对重金属离子的吸附能力与金属离子的性质及胶体种类无关。

[单选题]以下哪个土壤中的金属离子毒害性较小，对人体健康威胁较小（）？

[单选题]土壤中何种状态存在的重金属离子活性和毒性最大（）？

[单选题]土壤中何种状态存在的重金属离子活性和毒性最小（）？

[填空题]由土壤溶液中游离的氢离子所引起的酸度叫（），由土壤胶体所吸收的氢离子或铝离子所引起的酸度叫（）。

[多选题]能引起土壤酸性的离子有（）。

[名词解释题]潜性酸

[填空题]碱土的形成必须具备两个条件，一是有显著数量的钠离子进入土壤胶体，二是土壤胶体上交换性钠的（）。