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【单选题】
进行化学实验，观察实验现象．通过分析推理得出正确的结论是化学学习的方法之一．对下列实验操作和事实的解释正确的是（ ）A.
某学生用pH试纸测新制氯水的pH值，先变红后褪色，是因为Cl 2 有强氧化性
B.
加热碳酸氢钠固体，质量变轻，说明碳酸氢钠不稳定
C.
配制一定物质的量浓度溶液时发现浓度偏低，可能由于配制溶液所用的容量瓶事先未干燥
D.
将铜片放入浓硫酸中，无明显实验现象，说明铜在冷的浓硫酸中发生钝化
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举一反三
【多选题】一般来说，PID控制器参数微分系数Td与控制效果有密切关系，如下哪些说法是准确的。
A.
Td 也大，则有利于提高响应速度
B.
Td 的数值太大和太小都会引起超调
C.
Td 的可以取零值
D.
Td 取值与控制精度要求无关
【单选题】听力原文：W: This is too much. I have been waiting for my meal for more than half an hour. M: I know, but you see the restaurant is full and we're shorthanded today. Q: How does the woman feel? (15)
A.
She is satisfied.
B.
She is tired.
C.
She is impatient.
D.
She is happy
【单选题】Miss Sullivan tried to make Helen understand that "mug" is mug and "water" is water, but Helen kept confusing them, then Sullivan _________.
A.
dropped the subject once and for all
B.
continued to do it until she realized that her repeated attempts made Helen tired and angry
C.
became impatient and unhappy and gave it up
D.
dropped it for a while and picked it up when there was an opportunity
【简答题】Tired and impatient, we had a fight.
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