【单选题】测定SO2的质量分数,得到下列数据(%):28.62,28.59,28.51,28.52,28.61.质量信度为95%时平均值的置信区间为( )。(已知置信度为95%,n=5,t=2.776
【简答题】某同学设计实验以探究元素性质的递变规律,实验装置如图所示。 实验Ⅰ:根据元素最高价含氧酸的酸性强弱探究元素非金属性递变规律。 已知A装置的烧瓶里装有大理石,分液漏斗里装有稀HNO 3 ,B装置中装有饱和碳酸氢钠溶液,装置C中装有Na 2 SiO 3 溶液,试回答: (1)A中反应的离子方程式为____________________,C中可观察到的现象是________。 (2)B装置的作用是__...
【单选题】If you don't know a word, you can _____ it _____ in a dictionary. [ ]
【单选题】听力原文: With its 2X optical zoom lens, 3.2 megapixels and the size of a credit card, the Canon Digital Power-Shot S230 camera, introduced in September, 2002, might strike some as a marvel. But the compa...
A.
Similar to a credit card.
B.
Similar to a necklace.
C.
Similar to a cigarette box.
D.
Similar to a dressing case.
【简答题】某基础工程由挖地槽、做垫层、砌基础和回填土四个分项工程组成。该工程在平面上划分为六个施工段组织流水施工。各分项工程在各个施工段上的持续时间为4天。 问题: (1)流水施工有哪些种类? (2)根据该工程持续时间的特点,可按哪种流水施工方式组织施工? (3)什么是流水施工工期?该工程项目流水施工的工期应为多少天? (4)若工作面允许,每一段砌基础均提前一天进入施工,该流水施工的工期应为多少天?
【简答题】阅读理解。 Have you ever been at a meeting while someone was a speech and realized suddenly that your mind was a million miles away? You probably felt sorry and made up your mind to pay attention an...
【单选题】When you meet some new words, you can ____ in your dictionary. [ ]
【单选题】梁思成能成为一代建筑大师离不开其父亲梁启超的谆谆告诫,良好的家庭教育环境是梁思成人生发展中的顺境。对此,下列错误的观点是( )
【判断题】SN2反应是指卤代烃发生取代反应时,旧键的断裂和新键的形成是分两步进行的。
【单选题】— I don't know the new word. — It doesn't matter, you can _____ in the dictionary. [ ]