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【简答题】
Official figures give average class sizes as forty to fifty, but it is reported that in the rural areas there are often seventy to eighty children in a class．
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举一反三
【单选题】They were trying to remove harmful ______ from cigarettes.
A.
content
B.
substances
C.
materials
D.
mixtures
【简答题】A．blending B．associations C．combinations D．mixtures
【单选题】病人 , 张某,男, 50 岁,有慢性肾炎病史 20 年,最近出现水肿,皮肤瘙痒,少尿,每天尿量少于 400 ml , 口腔有氨臭味 ,发生口臭是由于
A.
细菌在口腔和咽部繁殖
B.
随 唾液排出的尿素被分解成 氨
C.
胃排空减弱
D.
大量 硫醇 排出
E.
丙酮排出增加
【单选题】Mixtures of chemicals that make a solution resistant to a change in pH are known as:
A.
amphoteric
B.
indicators
C.
electrolytes
D.
buffers
【简答题】mixtures
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