下列能源按形成和,不是来自太阳辐射能的是( )
A:煤和石油等矿物燃料
B:水能和生物能
C:潮汐能和地热能
D:风能
当别人称赞你时, 你应该说: “____”。
硫代硫醉钠又名”大苏打”,溶液具有弱碱性和较强的还原性,是棉织物漂白后的脱氯剂,定量分析中的还原剂.硫代硫酸钠(Na2S2O3)可由亚硫酸钠和硫粉通过化合反应制得,装置如图I所示.
已知:Na2S2O3在酸性溶液中不能稳定存在,有关物质的溶解度曲线如图2所示.
More than 6000 children were expelled(开除)from US schools last year for bringng guns and bombs to school,the US Department of Education said on May 8. The department gave a report on the expulsions(开除)as saying handguns accounted for 58 per cent of the 6093 expulsions in 1996—97,against 7 per cent for rifles or shotguns and 35 per cent for other types of firearms. “The report is a clear sign that our nation’s public schools are cracking down(严惩)”on students who bring guns to school,“Education Secretary Richard Riey said in a statement.“We need to be tough-minded(坚强的)about keeping guns out of our schools and do everything to keep our children safe.” In March 1997,an 11-year-old boy and a 13-year-old using hand-guns and rifles shot dead four children and a teacher at a school in Jonesboro,Arkansas.In October,two were killed and seven wounded in a shooting at a Mississippi school.Two months later,a 14-year-old boy killed three high school students and wounded five in Daducab,Kentucky. “Most of the expulsions,56 per cent,were from high schools,which have students from about age 13,34 per cent were from junior high schools and 9 per cent were from elementary schools.”The report said.