阅读下面短文，从短文后所给的A、B、C三个选项中选出能填入相应空白处的最佳选项。

     Karen spent more than 75 years working as a cleaner. Certainly nobody would think that she was rich, 1 she was paid only a few dollars each time. So they were all 2 when Jenny decided to give $150,000 to the University of Southern Mississippi.

    The money, 3, was her life savings. She could save such a large amount of money because she lived a very 4 life. She never learned to drive. When she wanted to go somewhere, she just walked. She never flew to anywhere 5 her donation（捐献）, and in the 50 years she had been out of the South only once. The 6 in which she lived was also a rather old one, and her last uncle left her. Only after she became known in 7 did she begin to travel all over the country. Since then, she had been the 8 of many interviews and articles. She was even invited to the White House.

    Her donation was for the students who clearly needed 9 help. She herself left school in the sixth grade and had never married or had children. She said to the reporters that the idea of helping somebody's child go to college gave her much 10.

其中，滤液A至滤液B之间需加入的三种试剂为：

试剂①：加入过量的X，除去滤液中的Ca²⁺

试剂②：加入过量的NaOH，除去滤液中的Mg²⁺

试剂③：加入过量的BaCl₂，除去滤液中的SO₄^2﹣

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