下列说法中,正确的是( )
A:不可能事件发生的概率为0
B:随机事件发生的概率为 12
C:概率很小的事件不可能发生
D:投掷一枚质地均匀的硬币100次,正面朝上的次数一定为50次
实验目的
实验操作
A
鉴别蚕丝制品和羊毛制品
用灼烧方法验证,闻是否有烧焦羽毛气味
B
检验淀粉水解的最终产物的还原性
取少量淀粉溶液,与稀硫酸共热后再加入银氨溶液,水浴加热,观察是否出现银镜
C
检验氯仿(CHCl3)中的氯元素
取少量氯仿加入硝酸银溶液,观察是否出现白色沉淀
D
除去乙酸乙酯中混有的少量乙酸
加入足量饱和Na2CO3溶液,振荡,静置,分液,取出上层液体
根据短文理解,从给出的A、B、C三个选项中选择最佳答案填空。
All parents love their children. Many parents want their kids to1 well-known people when they2 . Most of them want their kids to live better than others. Many of them 3their kids will be singers or actors. Actors and singers can 4 money easily in our country. When they appear in the advertisement, they will get 5 money which a farmer or a worker can't make all his life. Some of the parents want their kids to be businessmen6doctors. If they work hard, they will have cars and big houses in several 7. Some parents want their kids to work in cities and towns. They don't 8 them to work in the countryside. People who work in the cities and towns can get money after they 9. If you are a famous man, especially an actor, you'll get much but pay a little. A farmer is 10 , he gets little but pays much.