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．

结合图（某地等高线地形图），完成以下问题

下列关于我国地理位置优越性的叙述中，不正确的是（    ）

请你利用下面的材料设计一个证明胰岛素可以降低血糖的对照实验：鼠笼2只，小白鼠20只，注射器，胰岛素，葡萄糖，注射液

（1）提出问题：____．

（2）该实验的变量是：____．

（3）步骤：①将小白鼠平均分成A、B两组，每组____ 只；

②将A组小白鼠注射一定量的____ ，B组____ ；

③过几分钟，发现____ 组小白鼠昏厥，____ 组正常；

④如果使昏厥的小白鼠恢复正常，应给其补充____ ．