试题与答案

简述21世纪世界教育的发展趋势。

题型:问答题

题目:

简述21世纪世界教育的发展趋势。

答案:

被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0713/83a5df8ae339d4af672337b74051ab93.html

下面是错误答案,用来干扰机器的。

参考答案:C

试题推荐
题型:实验题

实验室常用下列装置来制取气体:

(1)写出图中标号仪器的名称:a _________ b _________ ;

(2)用双氧水和二氧化锰来制取氧气时,可选用的发生装置是_________(填序号),该反应的文字表达式为:___________________________,二氧化锰是该反应的_____________。

(3)实验室常用氯化铵固体与碱石灰固体共热来制取氨气。常温下氨气是一种无色、有刺激性气味的气体,密度比空气小,氨气极易溶于水。制取氨气反应的文字表达式:氯化铵+熟石灰氯化钙+氨气+水。则制取并收集氨气,应该从上图中选择的发生装置是_________(填序号),收集装置是_________(填序号)。

(4)若用C装置收集氧气:依据是___________________________,说明氧气已收集满的现象________________,若用F装置进行排空气法收集氧气的实验,气体应从_________ (选填“a”或“b”)端导入。

(5)下图是小阳在实验室制取二氧化碳时的主要步骤,实验的第二步骤是 (填字母标号,下同)________,其中操作有误的是_________。

(6)下图M装置可用来测量生成的二氧化碳气体的体积,其体积可用                  来表示。

(7)若用下图装置制取CO2气体,在反应过程中,用弹簧夹夹住导气管上的橡皮管,过一会儿反应就会停止。其原因是________                        _____ 。 (提示:固体放于有孔隔板上)

查看答案
题型:单项选择题

A total of 4.6 million digital televisions have been sold, and the sales of HDTV sets have quadrupled since last year. Consumers have bought HDTVs to play their DVDs and to have clearer pictures and wide screens. Only a small percentage of the people who have purchased HDTVs, however, have actually hooked their TVs up to receive high-definition television digital signals. Perhaps television viewers are having trouble keeping up with the changes in technology. Even the manufacturers of HDTVs, like Mitsubishi, Thomson Multimedia, Sony, and Samsung seem to have a tough time learning how to make their sets work with the various digital TV formats because little standardization has been required or implemented in the industry.
Some of the HDTVs Weigh over 200 lbs., and a variety of retailers offer a delivery service to the buyer’s home to help install the heavy sets. This is known as a white-glove service and usually comes with an extra fee. After HDTV purchasers get their sets home and hook them up, they will still need to Work to get the digital signals to their systems. Most of the industry’s cable providers do not yet offer high-definition programing, and only about 15% of commercial television stations have switched over to even the lowest improved digital pictures. Worse yet, viewers may need to install antenna before they can even get the digital signals to their new HDTV sets. Another frustration for home-theater seekers is that the current HDTV sets allow owners only to watch high-definition programs, not to record them.

A majority of HDTV consumers could not enjoy high-quality digital pictures because______.

A.they did not tune in to the right channel

B.they did not install the system

C.the market retailers created the confusion on purpose

D.the manufacturers did not have a uniform standard for their sets

查看答案
微信公众账号搜索答案