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【简答题】
论述韩国广播电视的发展概况。
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皮皮学刷刷变学霸
举一反三
【单选题】鉴别硝酸盐:取供试品溶液,置试管中,加等量的硫酸,小心混合,冷却后,沿管壁加 ( ) 试液,使成两液层,接界面显棕色
A.
氯化钡
B.
硫酸铁
C.
硫酸亚铁
D.
硫酸铜
E.
氯化汞
【单选题】鉴别硝酸盐:取供试品溶液,置试管中,加等量的硫酸,小心混合,冷却后,沿管壁加( )试液,使成两液层,接界面显棕色
A.
氯化钡
B.
硫酸铁
C.
硫酸铜
D.
硫酸亚铁
E.
硫酸铜
【单选题】Different Stages of Sleep A scientist who has spent many years studying sleep was asked this question: 'Why do we need sleep?' His answer was.'If we do not sleep, we get very sleepy, 'No one knows exa...
A.
If we do not sleep, we get very sleepy.
B.
Because there are four different stages of sleep.
C.
No one knows the cause.
D.
It is not mentioned in the article.
【单选题】鉴别硝酸盐:取供试品溶液,置试管中,加等量的硫酸,小心混合,冷却后,沿管壁加 ( ) 试液,使成两液层,接界面显棕色
A.
氯化钡
B.
硫酸铁
C.
硫酸铜
D.
硫酸亚铁
E.
氯化汞
【单选题】听力原文：M: Do you have any idea where Samuel is now? It's already 10: 30. This is the third time this week he's not on time. Didn't I make it clear that all waiters and waitresses must be at work by 10, ...
A.
He thinks Samuel is late again.
B.
Samuel has been late three days in a row.
C.
Samuel has to cut lawns in the morning.
D.
Samuel doesn' t have much experience.
【单选题】下列为苯甲酸盐的鉴别方法是 ( )
A.
取供试品的中性溶液，滴加三氯化铁试液，即生成赭色沉淀；再加稀盐酸，变为白色沉淀
B.
加 0.1 mol/L 亚硝酸钠溶液数滴，滴加碱性 β - 萘酚试液数滴，生成由橙黄到猩红色沉淀
C.
取供试品的中性溶液，加醋酸氧铀锌试液，即生成黄色沉淀
D.
取供试品少 量，置试管中，加等量的二氧化锰，混匀，加硫酸湿润，缓缓加热，产生的气体能使用水湿润的碘化钾淀粉试纸显蓝色
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