题干

某化工厂用软锰矿(含MnO2及少量Al2O3)和闪锌矿(含ZnS及少量FeS)联合生产Zn、MnO2,其部分生产流程如下:

已知:过滤(Ⅱ)所得滤液是MnSO4、ZnSO4、Fe2(SO43、Al2(SO43的混合液.相关金属离子生成氢氧化物沉淀的pH(开始沉淀的pH按金属离子浓度为1.0mol•L﹣1计算)如下表:

沉淀物

Fe(OH)3

Al(OH)3

Zn(OH)2

Mn(OH)2

开始沉淀时的pH

2.7

4.0

6.4

7.7

完全沉淀时的pH

3.7

5.2

8.0

10.4

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    Let children learn to judge their work.____ If corrected too much, he will stop talking. He notices a thousand times a day the difference between the language he uses and the language those around him use. Bit by bit, he makes the necessary changes to make the necessary changes to make his language like other people's.____They learn to do without being taught to walk, run, climb, whistle, ride a bicycle, compare their own performances with those of more skilled people, and slowly make the needed changes.

    But in school we never give a chance to find out his mistakes and correct them by himself.____ We act as if we thought that he would never notice a mistake unless it was pointed out to him, or correct it unless he was made to. Let him work out, with the help of other children if he wants it, what this word says, what the answer is to that problem, whether this is a good way of saying or doing this or not.

    If it is a matter of the right answer, as it may be in mathematics or science, give him the answer book.____Why should we teachers waste time on such routine work?____ Let the children learn what all educated people must some day learn, how to measure their own understanding, and how to know what they know or do not know.

A. Children leant to do all the other things in the same way.

B. Let him correct his own papers.

C. Point out his mistakes.

D. We do it all for him.

E. We allow him to learn from other children.

F. A child learning to talk does not learn by being corrected all the time.

G. Our job should be to help the child when he tells us that he can't find the way to get the right answer.