题干

I must leave now. I have to     goodbye to you.    

A:talk

B:tell

C:say

D:speak

上一题 下一题 0.0难度 选择题 更新时间:2019-09-05 11:11:15

答案(点此获取答案解析)

C

同类题2

阅读下则说明文,完成各小题。

中国助力“人造太阳”早日发光

    ①通过模仿太阳的热核聚变反应,中外科学家们正在建造人类首颗“人造太阳”。“人造太阳”计划,由欧盟、中国、美国等7大经济体联合打造,已历经30余年,预计2019年建成,2050年商用。

    ②上月底,中国承担生产和设计的首个超大部件——脉冲高压变电站(PPEN)首台主变压器,已运往“人造太阳”设施的建造地法国。随着各类设施逐渐完工,人类离建成首个“人造太阳”的目标越来越近。

    ③为什么要制造“人造太阳”?这和人类长久以来的能源危机有关。现代以来,随着人口增加、工业发展,人类对煤、石油、天然气等化石能源的消耗速度越来越快。据测算,人类最多还能用两三百年的自然能源,即使核能也只能用数百年。

    ④此外,像煤、石油这些能源的燃烧还会引发温室效应、酸雨等,对环境造成严重破坏;核电站或核能发电厂的能量来源是核裂变(能量产生过程与核聚变相反),所需原料稀有,产生的废料也没法安全处理,还可能产生核泄漏。

    ⑤不光我们这一代,我们的子孙将从哪里弄这么多能源呢?科学家们带着这个惊恐的问题,把目光投向了核聚变。天空中的太阳就是一个巨大的聚变体,几十亿年为人类提供了光、热。那太阳是怎么做的呢?

    ⑥简单来说,当两个质量较轻的原子核聚合为一个较重的新原子核时,大量电子和中子能够逃离原子核的束缚,带来巨大能量。在自然界中,最容易实现的聚变反应是氢的同位素——氘和氚的聚变。据测算,1千克氢燃料经过聚变反应所产生的能量,至少可以抵得上4千克铀燃料或1000万千克优质煤燃料释放的能量。

    ⑦要提取它们,方法也十分简便,成本也很低。我们从海水里舀一升水,其中就含有0.03克氘,它就可以产出约300公升汽油这么大的能量。地球上的海水能提取45万亿吨氘,它们都聚变的话,能保证人类上百亿年的能源消耗。

    ⑧而且核聚变非常干净,因为聚变就是把两个氢核放在一起,当温度到了上亿度以后,它们就会聚合在一起,除了产出能量,其余产出的氦是一种清洁无害的元素。

    ……

    ⑨前苏联科学家们设计了一种名为托卡马克的环形容器。通过让混合了氘、氚的气体悬浮在一个像面包圈一样的环中,然后不断加热,等达到了上亿摄氏度以后它就产生核聚变,并输出大部分能量。

    ⑩按照设计,“人造太阳”计划的反应堆设施总重量是埃菲尔铁塔的3倍,占地面积有60个足球场加起来那么大。这个反应堆建成后,能够把上亿摄氏度、由氘氚组成的“火球”约束在体积达837立方米的“面包圈”中,产生50万千瓦的聚变功率,持续时间达500秒。50万千瓦热功率已经相当于一个小型热电站的水平。

    ⑪截至目前,中国科学家已经攻克了采购包任务中遇到的所有技术难关。该计划两任总干事对中方的评价是“中国在采购包的研发、生产方面领先于各方”。

(选自2016年5月7日《人民日报》海外版,有删节)

同类题4

阅读下列四篇短文,从每小题后所给的A、B、C、D四个选项中,选出最佳选项,并在答题卡上将该选项涂黑。

    Elvis Presley,who was one of the most popular American singers of the twentieth century, made the Rock & Roll music popular around the world. He sold millions of records and made many successful films, and he helped change the direction of popular music in the 1960s.

Elvis Presley was born in a poor family in 1935. His parents were simple country people who often took him to church, where he learned to sing and he never forgot the kind of songs that he used to sing in church as a child.

    When he was a teenager, Elvis moved from Tupelos to Memphis in Tennessee, where he attended high school, but he was not a good student. His only real interest was singing. He began to sing in the style that is called “country and western”.

    In 1955 he recorded some songs for his mother's birthday. The people at the recording studio liked his singing and his music. There was something different about it. It was country and western music, but it also sounded a little like the music, which black people used to sing in the American South, music kn own as “blues”.

   Shortly after that, Elvis met Tom Parker, who became his manager and arranged(安排)concerts for him across the United States and new recordings as well. Soon Elvis rose to fame all over the country. Later, Elvis went to Hollywood and began to appear in films like Love Me Tender and King Creole.

    But Elvis found it hard to live with success, like many other entertainment personalities (娱乐圈内的人士). He began to take drugs and his health began to suffer. When he died at an early age of 42 in 1977, his many millions of fans were shocked. “The King Is Dead!” the newspaper said. But today his memory and his music live on and he will always be remembered as the King of Rock & Roll.