题干

将a组小麦培养于含18O的CO2的空气中,将b组小麦培养于含18O的O2的空气中,正常生长一段时间,a、b两组最先出现放射性氧的化合物依次是          (  )

C:五碳化合物和水

A:葡萄糖和二氧化碳

B:三碳化合物和水

D:三碳化合物和丙酮酸

上一题 下一题 0.0难度 选择题 更新时间:2019-06-20 01:04:49

答案(点此获取答案解析)

B

同类题3

阅读下面文字,完成下列小题。

“寒门再难出贵子”吗

    ①近几年来,“寒门再难出贵子”的说法时常见诸舆论。在例如顶级高校农村娃比例渐少、招聘市场越发偏爱城市青年的报道中,人们似乎发现,尽管中国人口素质、教育水平有了巨大提升,但物质条件、生活阅历方面的差距仍然是一大批“寒门青年”出人头地的障碍。情况是否如此有待验证,但“寒门再难出贵子”的社会焦虑却现实存在。

    ②谁才是今天社会中的“贵子”?富二代、官二代无疑符合传统意义上的“贵”,但如果没有一技之长,不能凭借自身本领干事创业,所谓“贵”也不过停留在人生的浅表。相反,白手起家的寒门青年,凭借自身努力打拼出一片天地,创造了属于自己乃至整个社会的价值,“贵子”的称谓自然当之无愧。作为哈佛大学优秀毕业生代表之一的中国寒门学子何江,曾讲到自己成功的经验:“每到一个更大的地方、更大的平台,你会发现自己不懂的东西很多,而我相对来说,好奇心比较多,我就会有压力去把它学会,让自己不断补足短处。”

    ③同时,网络文化高度繁荣的今天,寒门青年逆袭的方式也更加多元。之前,网名为“搬砖小伟”的湖北青年石神伟,凭借一系列自制的高难度健身视频,在短视频分享平台上吸引了超过百万粉丝。这位寒门青年从留守儿童、网瘾少年一路走来,用健身不断磨练和改变自己,传递着积极进取、拼搏向上的正能量,感动了无数网友。今天,许多像“搬砖小伟”这样寒门出身的“网红”,借助网络实现了自身的价值,也为社会进步传递着正能量。有人感慨,小伟的坚韧、低调和朴素,是这个时代的奢侈品,他是真正属于今天的“寒门贵子”。可以说,传播结构扁平化的互联网,为不少寒门青年打开了一扇改变人生的窗户,也创造了另外一种生命的可能。

    ④现代社会科学的研究表明,一个人的成功很大程度上与他拥有的社会信任和社会支持力量相关。家庭出身、教育背景和工作平台确实影响着一个人的成长路径。然而在价值多元化、传播渠道扁平化的今天,不仅“贵子”的意涵有了更为丰富的面向,同时由网络构成的“强大朋友圈”,也时常能为寒门青年走向成功提供强大的社会支持力量。

    ⑤一篇流行于网络的演讲词《寒门贵子》中,有这样一段话:“我们大部分人都不是出身豪门的,我们都要靠自己!所以你要相信:命运给你一个比别人低的起点是想告诉你,让你用你的一生去奋斗出一个绝地反击的故事。”这并不是鸡汤,而是说出了一个更为关键的问题:在今天这样一个充满无限可能的 时代,寒门能否出贵子,很大程度上并不是一个关于“命运”的话题,而是一个关于“奋斗”的故事。

(文章有删改)

同类题5

阅读理解

    In colleges around the country, most students are also workers. The reality of college can be pretty different from the images presented in movies and television. Instead of the students who wake up late, party all the time, and study only before exams, many colleges are full of students with pressing schedules of not just classes and activities, but real jobs, too.

    This isn't a temporary phenomenon. The share of working students has been on the rise since the 1970s, and one-fifth of students work year round. About one-quarter of those who work while attending school have both a full-course load and a full-time job. The arrangement can help pay for tuition (学费) and living costs, obviously. And there's value in it beyond the direct cause: such jobs can also be critical for developing important professional and social skills that make it easier to land a job after graduation. With many employers looking for students with already-developed skill sets, on-the-job training while in college can be the best way to ensure a job later on.

    But it's not all upside. Even full-time work may not completely cover the cost of tuition and living expenses. The study notes that if a student worked a full-time job at the federal minimum wage, they would earn just over $15,000 each year, certainly not enough to pay for tuition, room, and board at many colleges without some serious financial aid. That means that though they're sacrificing time away from the classroom, many working students will still graduate with at least some debt. And working full time can reduce the chance that students will graduate at all, by cutting into the time available for studying and attending classes.

    There is little reward for attending but not finishing college. Students who end up leaving school because of difficulty in managing work and class are likely to find themselves stuck in some of the same jobs they might have gotten if they hadn't gone at all. The difficulty of working too much while in school can create a cycle that pushes students further into debt without receiving any of the financial or career benefits.