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【简答题】
用双踪示波器观测两个同频率正弦波a，b，若扫描速度为20μs/cm，而荧光屏显示两个周期的水平距离是8cm，问： （1）两个正弦波的频率是多少？ （2）若正弦波a比b相位超前1.5cm，那么两个正弦波相差为多少？用弧度表示。
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【简答题】里面有（ ）个 ，有（ ）个 。
【单选题】Why does the author mention Father Christmas and the four horses of the Apocalypse'!
A.
To draw a parallel between the two.
B.
To show how fat people on earth are.
C.
To introduce the health risks in obesity.
D.
To make the text interesting.
【单选题】并励直流电机，采用电枢绕组串电阻调速方式，调速过程中保持负载不变，其则电枢电流、输入功率、输出功率、转速、励磁电流这几个变量中，保持不变的是（ ）。
A.
1
B.
2
C.
3
D.
4
【简答题】直流电动机按照主磁极绕组（又称励磁绕组）与电枢绕组连接方式的不同可分为[填空1]、[填空2]、[填空3]
【单选题】Why does the son think that his father is a tedious oddity?
A.
Because his father is the only parent who corrects his child's English.
B.
Because his father doesn't like grammar.
C.
Because he is allergic to his father's English.
D.
Because he is tired of listening to his father and doesn't like grammar.
【简答题】6里面有（ ）个 ，有（ ）个 ，有（ ）个 。
【简答题】120里面有______个十，700里有______个百，3000有______个千，400里面有40个______，84里面有______个十和______个一．
【单选题】Why does the son think of his father as a “tedious oddity”?
A.
Because his father is particular about how people talk about their travel experience.
B.
Because his father hardly chats with him about daily life.
C.
Because his father is very old-fashioned.
D.
Because his father talks a lot about grammar rules.
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