题干

某溶液中含有Ag+、Ba2+、Mg2+离子,为了将这三种离子逐个进行沉淀分离,加入下列离子的先后顺序正确的是(  )

A:CO32、Cl、OH

B:Cl、OH、CO32

C:OH、Cl、CO32

D:CO32、OH、Cl

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答案(点此获取答案解析)

B

同类题5

   Here is a 2-way student exchange. Fred, 19 , spent last year in Germany with George’s family. In turn, George’s son Mike spent a year in Fred’s home in America.
   Fred knew little German when he arrived. But after 2 months of studying, the language became easy for him. School was very different from what he had looked forward to and it was much harder. Students stood up politely when the teacher came into the room. They took 14 subjects while American students usually took 6 in the US.
   Family life, too, was different. The father’s word was the law(法律) . All the children had to do their activities with their family. Fred also missed having a car. In Germany, you should walk to go out to have a good time.
   At the same time, in America, Mike was forming his own ideas. He says,’ American schools are too easy for our level but I have to say that I like it a lot in Germany , we do nothing except study. Here we take part in many other activities.

Differences between American school life and German school life
ItemsAmerican studentsGerman students
Class rulesThey don’t have to stand up when their teacher come inThey have to ____  up and show respect(尊敬) to their ____ 
____  lifeThey do their own things alone.They have to listen to their ____ 
School ____ They have six and they are very easy for themThey have 14, but the lessons are much more ____ 
Going outThey can____  carsThey have to ____  all the way
School activitiesThey have ____  other activitiesThey have to ____  hard all the time.