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问题 选择题

下列物质的用途主要由其化学性质决定的是（　　）

A．用石墨做电极

B．用氢氧化钙改良酸性土壤

C．用石墨粉做润滑剂

D．用铁做成铁钉

答案

A、用石墨做电极利用了石墨的物理性质--导电性良好．故选项错误；

B、用氢氧化钙改良酸性土壤利用了氢氧化钙的化学性质--显碱性，能和显酸性的物质反应．故选项正确；

C、用石墨粉做润滑剂利用了石墨的物理性质--具有润滑性．故选项错误；

D、用铁做成铁钉利用了铁的物理性质--具有良好的延展性．故选项错误．

故选B．

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单项选择题

When I was seven years old my morn was diagnosed(诊断) with cancer. The doctors told us my morn might be saved with surgery(手术). But it could also kill her. She chose to have it.
The day before the surgery I was off school, and my mom planned the best day of my life, everything I loved at seven and everything that would put a smile on my lace. The day began with her waking me up saying, "Kate, I have a surprise for you. Come and see." The surprise was a doll I had wanted for the longest time. Throughout the day, she told my everything that she thought I would need to know to grow up and be a good person; she told me to be the best I could be and that I would always make her proud. We had a picnic in the park, and it was so cold that we moved to the car. The day was filled with laughter. For the first time in a long time I could see she was really happy. I would never forget her smile, or the way her eyes shone as if we were the same age. It was the best day of my life, and I will never forget the conversations we shared.
My mother managed to live through the surgery. Now when I look back, I realize that the best day of my life could be her last and this could be the last day I would remember with her, the last one we shared. I also understand how unselfish a mother is.

What did the writer’s mother do the day before the surgery

A．She stayed at home to have a good rest.

B．She went to the doctor’s for advice.

C．She turned to her family for comfort.

D．She stayed all day with her chil
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