P（u﹣σ＜X≤u+σ）=0.6826，

P（u﹣2σ＜X≤u+2σ）=0.9544

P（u﹣3σ＜X≤u+3σ）=0.9974，

一班有60名同学，一次数学考试的成绩服从正态分布，平均分110，方差为100，理论上说在120分到130分之间的人数约为（   ）

阅读短文，判断正误。正确的写“正确”，错误的写“错误”。

B

     It is Sunday morning.Mr. Brown and his son, Bill, are in a big shopping mall. Mr. Brown wants to buy a new dress for Mrs. Brown. Bill likes oranges. So his father buys two kilos of oranges for him, too. There are many things and many people in the mall. There are men and women, old and young. They all want to buy something there. The people in the mall are friendly. They are glad to help you find what you are looking for.

某同学欲证明露置在空气中的苛性钠的变质程度，其所选用的试剂、操作方法、现象和结论均正确的是（　　）