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【单选题】
为了除去粗盐中含有的 Ca 2 + 、 Mg 2 + 、 SO 4 2 - 及泥沙,得到纯净的 NaCl ,可将粗盐溶于水,然后在下列操作中选取必要的步骤和正确的操作顺序: 1 过滤; 2 加过量 NaOH 溶液; 3 加适量盐酸; 4 加过量 Na 2 CO 3 溶液; 5 加过量 BaCl 2 溶液A.
⑤②④③①
B.
④①②⑤③
C.
②⑤④①③
D.
①④②⑤③
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举一反三
【单选题】The underlined term 'life expectancy' (Para. 1) refers to______.
A.
the length of time for each person
B.
the expectations of a person's life
C.
the seasonal changes in a person's life
D.
the average period that a person may expect to live
【单选题】As an ______ (someone who sets up a business venture), your personal life and business life are interconnected. (Para. 10)
A.
entrepreneur
B.
investigator
C.
subscriber
D.
navigator
【简答题】TLF文本包括3种类型的文本块,它们是只读、可选和可编辑。文本有俩种排列方向,它们是()和()
【单选题】Life in the countryside is quite ____ that in modern cities. [ ]
A.
the same
B.
different from
C.
full of
【单选题】回答下列各题 (II) I am discovering that many people want, above all else, to live life fully. But sometimes the past prohibits our living and enjoying life to the utmost in the present. A school teacher 26 ...
A.
entered
B.
left
C.
rushed
D.
slipped
【单选题】According to Para. 2, the writer thinks that______.
A.
life for a child is comparatively easy
B.
a child is always loved whatever he does
C.
if much is given to a child, he must do something in return
D.
only children are interested in life
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