问题
选择题
有两种物质的量浓度相等的溶液，把它们等体积混合有白色沉淀生成，加入过量稀HNO3后，沉淀消失并放出气体，再加入AgNO3溶液又有白色沉淀生成，这两种溶液是 （ ）
A．Na2CO3和Ca(OH)2
B．Na2CO3和CaCl2
C．NaOH和CuSO4
D．Na2SO4和Ba(NO3)2
答案
答案：B
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有两种物质的量浓度相等的溶液，把它们等体积混合有白色沉淀生成，加入过量稀HNO3后，沉淀消失并放出气体，再加入AgNO3溶液又有白色沉淀生成，这两种溶液是 （ ）
A．Na2CO3和Ca(OH)2
B．Na2CO3和CaCl2
C．NaOH和CuSO4
D．Na2SO4和Ba(NO3)2
答案：B
Tong Shiqiang rushed into a kindergarten behind his primary school several times, carrying a __36__ of kids each time he rushed out of their classroom on that fateful（灾难的）day. Only 14 years old and 1.5m tall, Tong can now __37__ a national bravery award for saving seven children. The grade-6 student was __38__ a Chinese language class in Zhongwang Primary School in Qishan village of Longnan city, one of the worst-hit areas in Gansu province, __39__ the deadly quake struck on May 12,2008. There were 49 __40__ students in his class at the time. "Windows began rattling(嘎嘎响）and it __41__ as if lots of bees were singing underground," __42__ Tong Shuangxi, Tong Shiqiang’s teacher and uncle. "The sound grew __43__ ... and then I __44__ it was an earthquake." The teacher cried: " __45__ out!" All the students ran out of the room immediately. __46__ outside, Tong Shuangxi rushed toward the kindergarten where the children __47__ a nap (午睡). Tong Shiqiang ran with him. Only three of the kids had __48__ to run out of their room when they __49__ the building. The rest were crying, too __50__ to move. It __51__ less than three minutes for them to carry out all the five- and six-year-olds to __52__. __53__ whether all the kids had been saved, Tong and his nephew had __54__ begun checking the name list when the classroom’s walls fell down. "That’s the only time I was scared," said Tong Shiqiang. The 14-year-old is __55__ to be nominated (提名) for the child hero award, to be given by the Ministry of Education and the Central Committee of the Chinese Communist Youth League.
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