萃取过程中选择有萃取剂要遵循的原则()。A、萃取率要高,选择性要好,萃取后易被反萃B

题型:多项选择题

问题:

萃取过程中选择有萃取剂要遵循的原则()。

A、萃取率要高,选择性要好,萃取后易被反萃

B、在水中的溶解度小、粘度和比重小,分相快

C、沸点高,挥发小,毒性腐蚀性小,容易制备且价格低

考点:硫酸镍生产工硫酸镍初级工硫酸镍初级工题库
题型:多项选择题

阅读理解。

     Dick was born in a poor family. His father had a small boat and went fishing in the morning and sold

the fish in the market in the afternoon. Then he bought some food for his family. When winter came, they

were often hungry. One morning the hungry man fell into the river and wasn't found. Dick's mother left

her three-year-old son without saying good-bye. His aunt had to look after him.

     Twenty years passed. Dick became a tall, strong man. He found work on a farm. He worked hard

and wanted to get more money. He often went to see his aunt with some nice presents. The woman was

very happy but one day she died in a traffic accident. The young man was very sad. After he buried her,

he decided to buy a beautiful tombstone(墓碑)for her. He went to town and came in a shop, but all the

tombstones were too expensive. He asked, "Do you sell an old tombstone, sir?" "Yes, we do, sir, "

answered the shopkeeper. "Is it as expensive as the new one?"

     "No, it's much cheaper," said the man. "But another name was engraved (刻) on it." "It doesn't matter,

" said Dick. "My aunt couldn't read. "

1. If     ___ , the family members were hungry.

A. Dick's father could catch no fish in winter  

B. Dick's father had a boat in winter

C. Dick's father had to look after him in winter  

D. no food was sold in winter

2. The woman had to look after Dick because  __     .

A. she was rich            

B. his father asked her

C. she was kind-hearted    

D. the boy loved her

3. Dick wanted to get more money to     __ .

A. marry a wife            

B. give his aunt nice presents

C. buy a farm              

D. build a house

4. Dick often went to see his aunt because       _ .

A. she felt lonely          

B. she was often ill

C. she had no children      

D. with her help he grew up

5.Dick wanted to buy an old tombstone because  __  _ .

A. he had enough money to buy a new one

B. his aunt couldn't read whose name was engraved

C. his aunt wasn't going to mind it    

D. nobody knew what his aunt's name was

题型:多项选择题

城市布局主要有()两种基本形式。

A.多中心布局和单中心布局

B.组团布局和星状布局

C.带状布局和环状布局

D.集中布局和分散布局

题型:多项选择题

场外交易市场即是指店头市场。( )

题型:多项选择题

分布式数据库中定义数据分片时,必须满足3个条件:完备性条件、重构条件和______。

题型:多项选择题

当采用综合接地方法时,扩声系统接地应采用专用线与其可靠连接,接地线应采用多芯绝缘电缆,线芯截面面积不应小于()m2。

A.10

B.16

C.25

D.35

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