mooc答案类别订阅

计算机中数值数据的表示随堂测验

1、单选题：
‍将二进制数1010101101.1转换成十六进制数为                。  ‏
选项：
A: 2AD.1H
B: 2AC.8
C: 2AC.4 
D: 2AD.8
答案: 【 2AD.8】点我阅读全文

Scanning

1、单选题：
‌Read the passage "The Discovery of X-rays" quickly and choose the paragraph(s) which contain(s) the answer(s). You may choose more than one answer for question 3. ‌‌‌The Discovery of X-rays‌‌ ‌Par. 1 Except for a brief description of the Compton effect, and a few other remarks, we have postponed the discussion of X-rays until the present chapter because it is particularly convenient to treat X-ray spectra after treating optical spectra. Although this ordering may have given the reader a distorted impression of the historical importance of X-rays, this impression will be corrected shortly as we describe the crucial role played by X-rays in the development of modern physics.‌Par. 2 X-rays were discovered in 1895 by Roentgen while studying the phenomena of gaseous discharge. Using a cathode ray tube with a high voltage of several tens of kilovolts, he noticed that salts of barium would fluoresce when brought near the tube, although nothing visible was emitted by the tube. This effect persisted when the tube was wrapped with a layer of black cardboard. Roentgen soon established that the agency responsible for the fluorescence originated at the point at which the stream of energetic electrons struck the glass wall of the tube. Because of its unknown nature, he gave this agency the name X-rays. He found that X-rays could manifest themselves by darkening wrapped photographic plates, discharging charged electroscopes, as well as by causing fluorescence in a number of different substances. He also found that X-rays can penetrate considerable thicknesses of materials of low atomic number, whereas substances of high atomic number are relatively opaque. Roentgen took the first steps in identifying the nature of X-rays by using a system of slits to show that (1) they travel in straight lines, and that (2) they are uncharged, because they are not deflected by electric or magnetic fields.‌Par. 3 The discovery of X-rays aroused the interest of all physicists, and many joined in the investigation of their properties. In 1899 Haga and Wind performed a single slit diffraction experiment with X-rays which showed that (3) X-rays are a wave motion phenomenon, and, from the size of the diffraction pattern, their wavelength could be estimated to be 10-8 cm. In 1906 Barkla proved that (4) the waves are transverse by showing that they can be polarized by scattering from many materials.‌Par. 4 There is, of course, no longer anything unknown about the nature of X-rays. They are electromagnetic radiation of exactly the same nature as visible light, except that their wavelength is several orders of magnitude shorter. This conclusion follows from comparing properties 1 through 4 with the similar properties of visible light, but it was actually postulated by Thomson several years before all these properties were known. Thomson argued that X-rays are electromagnetic radiation because such radiation would be expected to be emitted from the point at which the electrons strike the wall of a cathode ray tube. At this point, the electrons suffer very violent accelerations in coming to a stop and, according to classical electromagnetic theory, all accelerated charged particles emit electromagnetic radiations. We shall see later that this explanation of the production of X-rays is at least partially correct.‌Par. 5 In common with other electromagnetic radiations, X-rays exhibit particle-like aspects as well as wave-like aspects. The reader will recall that the Compton effect, which is one of the most convincing demonstrations of the existence of quanta, was originally observed with electromagnetic radiation in the X-ray region of wavelengths.‌‌‌‌When were X-rays discovered?‌
选项：
A: Par. 1
B: Par. 2
C: Par. 3
D: Par. 4
E: Par. 5
答案: 【 Par. 2】点我阅读全文

1.1.1二、三阶行列式(随堂测验

1、单选题：

‌

‎选项：
A:
B:
C:
D:
答案: 【 】点我阅读全文

第一章绪论测试

1、单选题：
食品毒理学是研究（       ）的一门科学。‎‎
选项：
A: 食品中微生物毒素的产生机制，并确定这些物质的安全限量和评定食品安全性
B: 食品中真菌毒素的毒作用机制，并确定这些物质的安全限量和评定食品安全性
C: 食品中的外源化学物的不良作用及机制，并确定其安全限量和评定食品安全性
D: 食品中多环芳烃毒作用机制及其防护措施
答案: 【 食品中的外源化学物的不良作用及机制，并确定其安全限量和评定食品安全性】点我阅读全文

第一单元《身体运动功能训练概述》测验题

1、单选题：
‍从训练内容来看，身体运动功能训练不包括：‏
选项：
A: 功能动作筛查（FMS）
B: 动作准备
C: 快速伸缩复合练习
D: 专项技术训练
答案: 【 专项技术训练】点我阅读全文

第一周单元测验

1、单选题：
‎运-20是中国依靠自己力量研制的一种（  ）吨级大型、多用途运输机。​
选项：
A: 100
B: 150
C: 200
D: 220
答案: 【 200】点我阅读全文

测验

1、判断题：
‌ 会计是一种经济管理活动。（    ）‎
选项：
A: 正确
B: 错误
答案: 【 正确】点我阅读全文

随堂测验1

1、单选题：
‎4.植物的营养器官不包括：（）‎
选项：
A: 根
B: 茎 
C: 叶
D: 种子
答案: 【 种子】点我阅读全文

第一单元测试

1、单选题：
‌下列不能反映《雨巷》中诗人内心的选项是：‎
选项：
A: 愉悦明朗 
B: 混沌迷惘
C: 孤独寂寞
D: 忧愁苦闷
答案: 【 愉悦明朗 】点我阅读全文

Unit 1 单元测试

1、单选题：
In number of native speakers and language learners, English is the ________ language in the world.‏‎‏
选项：
A: first
B: second
C: third 
D: fourth 
答案: 【 first】点我阅读全文