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【单选题】
原子发射光谱是由下列那种跃迁产生的?A.
辐射能使气态原子外层电子激发
B.
辐射能使气态原子内层电子激发
C.
电热能使气态原子内层电子激发
D.
电热能使气态原子外层电子激发
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A.
it is
B.
I am
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this is
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he is
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What's your name
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will rain: had
B.
is raining; have had
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rains; had
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is going to rain; have had
【简答题】A: Do you know this welding equipment ? B: Yes. It is a wire feeder. A: Could you say more about it? B: Sure. This is the handle . This is the wire reel . This is the wire drive-roll . This is the con...
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