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问题 问答题

由海水晒得的粗盐中含有一些泥沙杂质．设计实验，除去粗盐中的泥沙，得到较纯净的精盐．

答案

①溶把粗盐放入烧杯中，加水溶解；

②过滤；架好漏斗，使漏斗下端口紧贴烧杯内壁，沿玻璃棒把上述悬浊液慢慢导入漏斗中；

③蒸发结晶：将上述滤液倒入蒸发皿中，用酒精灯加热蒸发．

单项选择题

钢筋绑扎最常用的方法是（）。

A、十字花扣

B、一面顺扣

C、套扣

D、兜扣
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单项选择题

For users, microkernel technology promises (90) , compact and sophisticated operating systems that are typically (91) across a range of hardware platforms. These operating systems will be customizable to let users run multiple operating system and application "personalities" on top of a single microkernel (92) .
Microkernel based systems can provide this flexibility because the core operating system functions are (93) from the large number of utilities, features and extensions that are layered on top of them. As a result, updating and maintaining operating system is easier, since developers don’t have to modify the (94) every time they must acid a new feature.

A．core

B．center

C．heart

D．utility
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