Passage Three
In 2008，the United States Department of Agriculture(USDA)wanted to know if all the school lunches served to students were healthy．The answer was a big，fat NO!
The USDA found that most American schools served lunches with too much fat and salt．They also found that most of the fruits and vegetables in the lunches came from cans(罐头)．Canned fruits and vegetables are not as good as fresh ones．
The USDA gives schools food and money to make lunches．But schools make up their own menus．Some make healthy lunches．Most do not．Now the USDA wants all schools to serve more healthy lunches．They want schools to follow the USDA’s guidelines for balanced(均衡)meals．
Mike Sanders，in charge of the USDA in 2008，said the USDA should teach school workers how to make healthier lunches．“A good school lunch is just as important as a good textbook，”Sanders said．He said that children also need to learn about healthy foods．
The USDA is working on a new program--Fresh Start．It will give schools more fresh fruits and vegetables．Fresh Start will also help schools change their lunches to make them healthier．To find the best way to change lunches，the USDA held meetings with parents，school leaders，doctors，and cooks．
Children already eat healthy lunches at Chief Joseph School in North Saratoga，Oregon．They have whole-wheat bread with low-fat cheese, and low-fat milk．
What was Mike Sanders?
把10gMgCl2和MgSO4的混合物溶于适量水中，滴加2mol／L的BaCl2溶液至沉淀完全，共消耗BaCl2溶液25mL。求混合物中MgCl2和MgSO4的质量各是多少克
固定在匀强磁场中的正方形导线框abcd，各边长为1．其中ab是一段电阻为R的均匀电阻丝，其余3边均为电阻可忽略的铜线。磁场的磁感应强度为B，方向垂直纸面向里。现有一与ab段的材料、粗细、长度都相同的电阻丝PQ架在导体框上，如图所示。PQ以恒定速度方向如何
一小物块以速度v0=10m／s沿光滑地面滑行，然后沿光滑曲面上升到顶部水平的高台上，并由高台上飞出，如图所示。问当高台的高度h多大时，小物块飞行的水平距离最大这个距离是多少(g=10m／s2)
某晶体盐的水溶液呈浅绿色，在此溶液中通入氯气，溶液变为棕黄色，把所得棕黄色溶液分成两份：一份加入KSCN溶液，溶液变深红色；另一份加入BaCl2溶液，产生不溶于稀HNO3的白色沉淀，则该晶体盐的化学式是_______。
欲除去乙烷中的乙烯，可将混合气体通过盛有_______的洗气瓶；欲除去乙炔中的硫化氢，可将混合气体通过盛有_______的洗气瓶。
浓硝酸常盛装在棕色瓶中，且贮放在冷暗处，原因是_______，
碳酸氢钠溶液和烧碱溶液反应的离子方程式为_______。
常温下，氨水中存在的离子有_______。
在酸或碱存在的条件下，甲酸甲酯跟水发生水解反应的化学方程式为_______。
有下列几种气体：H2、O2、HCl、NO、NH3、CH4，其中通常情况下能用来和水做“喷泉”实验的是_______。
