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问题
单项选择题
能改善混凝土的和易性，提高混凝土抗冻融耐久性的外加剂是( )。
A．减水剂
B．早强剂
C．引气剂
D．缓凝剂
答案
参考答案：C
选择题
—May I speak to Mr Smith?
—Sorry, he ____ Australia. But he ____ in two days.
A. has been to; will come back
B. has gone to; will be back
C. has been in; would come back
D. is leaving for; doesn't come back
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填空题
因素分析包括（）数和（）数分析。
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