【单选题】You should frequently compare drum-mounted and remote-reading water level indicators_____ between these have contributed to failures because of overheating through shortage of water, when a boiler was...
【简答题】啤酒是生活中常见的饮料,其中含有CO 2 、H 2 O、蛋白质等物质.为研究啤酒的相关问题,现进行如下实验: (1)观察一瓶啤酒,未见气泡;打开啤酒瓶盖,会冒出大量气泡,原因是 ______.使啤酒的气泡快速放出的方法有搅拌、振荡、______等. (2)为验证放出的气泡是CO 2 ,你的实验方法是 ______.
【单选题】Why did the writer compare reading a thick book to a building?
A.
Both of them need time.
B.
Both of them have precise structures.
C.
Both of them need imagination.
【简答题】某研究性学习小组就Na 2 O 2 的有关性质探究如下:向滴有酚酞的水中投入一定量的Na 2 O 2 ,观察到先有大量气泡产生,溶液变红,过一会儿溶液又变为无色。 对上述实验中溶液变红,过一会儿又褪色的原因,甲、乙两同学提出了不同的解释: 甲同学认为是Na 2 O 2 与水反应放出氧气,氧气有氧化性,将酚酞氧化而使溶液褪色; 乙同学则认为是Na 2 O 2 与水反应时产生了H 2 O 2 ,H 2...
【单选题】Why did the writer compare reading a thick book to a building?
A.
Both of them need time.
B.
Both of them have precise structures.
C.
Both of them need imagination.
【判断题】从空间角度观察,需要研究旅游系统客源地和目的地之间的相互作用,包括旅游者从O到D之间的移动,即“O—D对”。
【单选题】表示血型(A.B.AB.O型)的资料,该资料为()。 A.观察单位 B.数值变量