混凝土采用覆盖浇水养护的时间的要求中,对掺用缓凝型外加剂、矿物掺合料或有抗渗性要求的混凝土,不得少于(  )d。

混凝土采用覆盖浇水养护的时间的要求中,对掺用缓凝型外加剂、矿物掺合料或有抗渗性要求的混凝土,不得少于(  )d。A.7 B.14 C.21 D.30

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Historical evidence shows that birth and death rates level

Historical evidence shows that birth and death rates level off as countries mov

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To prevent viruses from spreading, we should______________

To prevent viruses from spreading, we should______________A.shake hands with ou

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It' s about two hour' s (fly) ______________ from Xi' an to

It' s about two hour' s (fly) ______________ from Xi' an to Beijing.

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A.give B.suggest C.take D.leave

A.give B.suggest C.take D.leave

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