接触镜的镜面负离子基团可吸引泪液中带有正电荷的（）离子，并进一步结合沉淀物。
A、钾
B、氯
C、钠
D、钙
参考答案：D
什么是气缸工作容积？
把下列各句翻译成汉语。
①Stop arguing about procedure and get down to business.
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②Let's proceed to business.
③He proceeded to inform me that everything was wrong with it．
