根据下面资料，回答39-42题
Nancy wanted to make good use of her spare time. So she decided to work for the underdog. For the past several years, she has been putting her experience and energy to help a disadvantaged( 条件差的 ) high school student.
Nancy knew that her knowledge would be best shared in a one-to-one situation. She found her perfect match in Operation Jump Start (OJS).
OJS was founded in 1994 in Long Beach, California, with the goal of helping students reach for higher education. It pairs students with experienced volunteers (志愿者), and provides them with workshops on writing, leadership development, and guided tours of various colleges.
Since its start, OJS has helped 80 students graduate from high school, with 95 percent moving on to higher education.
Nancy and the girl, Yanira, spent most of their time on school work. Together the two often went to museums, zoos, the movies, and concerts; they even sang in the school holiday show together!
“I know I′ m not like anyone else in Yanira′ s life,” Nancy says, “It′ s been great to get to know her and to watch her change, grow, and learn. ”
Much to Nancy′ s excitement, Yanira plans to attend John Jay College in New York City, where Nancy′ s father taught for his whole life. "These days I share her dream, and if she gets accepted I hope to travel to New York with her and show her around," Nancy says.
The word "underdog" in Paragraph 1 probably refers to____________
推理判断题。根据第一段可知，为了充分利用课余时间，南希在过去的几年里一直在帮助一名高中差生。由此推断出underdog指的是需要他人在学业上予以帮助的学生。故本题选c。
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_______。
