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【单选题】
离子交换树脂去除硬度的原理是,通过离子交换树脂上可用来交换的( )离子,把水中的( )离子交换上去,置换下来离子交换树脂上原有的这些可活动可交换的阳离子到溶液中,正确选项为( )A.
阳； 钙、镁离子
B.
阴； 钙、镁离子
C.
阳； 钠离子
D.
阴； 铝离子
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【简答题】When he arrived home early,he would cook meals for his family.
【简答题】It was()he arrived home()he realized that he had left his keys in the office. A) until……that B)not until……had C) until……had D)not until……that
【判断题】The Spring Festival isin accordance with the solar term of the beginning of spring, which is a time offresh beginning.
A.
正确
B.
错误
【简答题】had he arrived home than it began to rain．
【单选题】Not until he arrived home _____ he find that this wallet had been stolen.
A.
did
B.
would
C.
when
D.
that
【判断题】In Chinese “24 Solar Terms”, the beginning of a new year, is called the “Beginning of Spring”.
A.
正确
B.
错误
【单选题】Only when he arrived home _____ that he had left his key in the office.
A.
will he realize
B.
he did realize
C.
did he realize
D.
should he realize
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