题干

在一个密闭容器中放入甲、乙、丙、丁四种物质,在一定条件下发生化学反应,一段时间后,测得有关数据如下表:下列说法中,正确的是(  )

物质

反应前质量/g

18

1

2

32

反应后质量/g

X(未知)

26

2

12


A:反应后物质甲的质量X为5

B:乙是反应物

C:物质丙一定是该反应的催化剂

D:反应中乙、丁的质量比为5:4

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答案(点此获取答案解析)

D

同类题1

读文章,完成文后练习。

陈毅弈棋

    无产阶级革命家、军事家陈毅同志,一生多才多艺,常常在战斗和工作之余,不是赋诗以抒情怀,就是弈棋以调节身心,驱除疲劳。∥

    任新四军军长的陈毅,在苏中战斗打响后,住在苏北根据地的一个村子里。一次,他从战士那里得知村里的一位私塾先生很善下棋,便趁空闲时间只身徒步走到私塾拜访。老先生说:“我同本乡人下棋,从不动‘将’;今天你是客人,我得破例了。”于是两人对弈起来。最后,陈毅以一胜二平的比数获胜。

    过了一段时间,陈毅带领部队来村子里休整,又去找那先生下棋。这次先生声明不动“将”,与陈毅厮杀起来,结果陈毅以零比三连输三局。陈毅诧异地问:“老先生,前次你动了‘将’,我赢了;这次你‘将’不动,我反而连输三局,不知何故?”老先生答道:“前次来,我知道你是首长,又在出征前夕,不可挫其锐气;这次,我知道你在战场上取了大胜,而我在‘战场’上要使你连败三局,让你冷静一下大脑。”∥

    回忆起这件事,陈毅写了一首诗:“九牛一毫莫自夸,骄傲自满必翻车。历览古今多少事,成由谦虚败由奢。”∥

【注释】①九牛一毫:(成绩)犹如牛身上的一根毫毛,比喻微不足道。②历览:纵观;经过以往许多次的观察研究。③奢:过高地估计自己,指骄傲。

同类题2

阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项。

    The world's most human-like robot has begun work as a university receptionist. And scientists positively predict the new technology will 1 provide childcare and offer 2 to lonely elderly people.

    With her soft skin and flowing dark-brown hair, Nadine does not only meet and greet3, smile, make eye contact and 4 hands, but she can even5 past guests and get into conversation based on 6 chats.

    Unlike 7 robots, Nadine has her own personality and 8 . She can be happy or sad, 9 on the topic.

    Powered by intelligent 10 similar to Apple's Siri or Microsoft's Cortana, she is the creation of scientists at the Nanyang Technological University in Singapore and is based on her creator Prof Nadia Thalmann.

    Prof Thalmann, the director of the Institute for Media Innovation who led the development said robots such as Nadine are bound to become more visible in offices and 11 in future.

    “Robotics technologies have 12 significantly over the past few decades and are already being used in manufacturing and logistics,” she said.

    “As countries worldwide face 13 of an aging population, 14 robots can be one solution to 15 the shrinking(缩小的) workforce, become personal 16 for children and the elderly at home, and 17 serve as a platform for healthcare services in future.”

    “Over the past four years, our team at NTU have been 18 cross-disciplinary(跨学科的) research in social robotics technologies— involving engineering, computer science, linguistics, psychology and other19 — to transform a virtual human(虚拟的人), from within a computer, into a 20 being that is able to observe and interact with other humans.”