题干

关于化学反应速率的说法正确的是(   )

A:化学反应速率可表示反应进行的程度

B:化学反应速率是指一定时间内,任何一种反应物浓度的减少或任何一种生成物浓度的增加

C:对于任何化学反应来说,活化分子越多,反应速率越快,反应现象就越明显

D:决定化学反应速率的主要因素是参加反应的物质的性质

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D

同类题1

阅读下面的文章,完成小题。

丑石

贾平凹

    ①我常常遗憾我家门前的那块丑石呢:它黑黝黝地卧在那里,牛似的模样;谁也不知道是什么时候留在这里的,谁也不去理会它。只是麦收时节,门前摊了麦子,奶奶总是要说:这块丑石,多碍地面哟,多时把它搬走吧。

    ②于是,伯父家盖房,想以它垒山墙,但苦于它极不规则,没棱角儿,也没平面儿;用錾破开吧,又懒得花那么大气力,因为河滩并不甚远,随便去掮一块回来,哪一块也比它强。房盖起来,压铺台阶,伯父也没有看上它。有一年,来了一个石匠,为我家洗一台石蘑,奶奶又说:用这块丑石吧,省得从远处搬动。石匠看了看,摇着头,嫌它石质太细,也不采用。

    ③它不像汉白玉那样的细腻,可以凿下刻字雕花,也不像大青石那样的光滑,可以供来浣纱捶布;它静静地卧在那里,院边的槐荫没有庇覆它,花儿也不再在它身边生长。荒草便繁衍出来,枝蔓上下,慢慢地,竟锈上了绿苔、黑斑。我们这些做孩子的,也讨厌起它来,曾合伙要搬走它,但力气又不足;虽时时咒骂它,嫌弃它,也无可奈何,只好任它留在那里去了。

    ④稍稍能安慰我们的,是在那石上有一个不大不小的坑凹儿,雨天就盛满了水。常常雨过三天了,地上已经干燥,那石凹里水儿还有,鸡儿便去那里渴饮。每每到了十五的夜晚,我们盼着满月出来,就爬到其上,翘望天边;奶奶总是要骂的,害怕我们摔下来。果然那一次就摔了下来,磕破了我的膝盖呢。

    ⑤人都骂它是丑石,它真是丑得不能再丑的丑石了。

    ⑥终有一日,村子里来了一个天文学家。他在我家门前路过,突然发现了这块石头,眼光立即就拉直了。他再没有走去,就住了下来;以后又来了好些人,说这是一块陨石,从天上落下来已经有二三百年了,是一件了不起的东西。不久便来了车,小心翼翼地将它运走了。

    ⑦这使我们都很惊奇!这又怪又丑的石头,原来是天上的呢!它补过天,在天上发过热,闪过光,我们的先祖或许仰望过它,它给了他们光明,向往,憧憬;而它落下来了,在污土里,荒草里,一躺就是几百年了?

    ⑧奶奶说:“真看不出!它那么不一般,却怎么连墙也垒不成,台阶也垒不成呢?”

    ⑨“它是太丑了”。天文学家说。

    ⑩“真的,是太丑了”。

    ⑪“可这正是它的美”天文学家说,“它是以丑为美的。”

    ⑫“以丑为美?”

    ⑬“是的,丑到极处,便是美到极处。正因为它不是一般的顽石,当然不能去做墙,做台阶,不能去雕刻,捶布。它不是做这些玩意儿的,所以常常就遭到一般世俗的讥讽。”

    ⑭奶奶脸红了,我也脸红了。

    ⑮我感到自己的可耻,也感到了丑石的伟大;我甚至怨恨它这么多年竟会默默地忍受着这一切?而我又立即深深地感到它那种不屈于误解、寂寞的生存的伟大。

同类题3

阅读理解

    If English means endless new words, difficult grammar and sometimes strange pronunciation, you are wrong. Haven't you noticed that you have become smarter since you started to learn a language?

    According to a new study by a British university, learning a second language can lead to an increase in your brain power. Researchers found that learning other languages changes grey mater. This is the area of the brain which processes information. It is similar to the way that exercise builds muscles.

    The study also found the effect is greater when the younger people learn a second language. A team led by Dr. Andrea Mechelli, from University College London, took a group of Britons who only spoke English. They were compared with a group of bilinguals who had learnt a second language before the age of five, as well as a number of later learners.

    Scans showed that grey mater density(密度) in the brain was greater in bilinguals than in people without a second language.

    “Our findings suggest that the structure of the brain is changed by the experience of learning a second language,” said the scientists. It means that the change itself increases the ability to learn.

    Professor Dylan Vaughan Jones of the University of Wales, has researched the link between bilingualism and maths skills. “Having two languages gives you two windows on the world and makes the brain more flexible,” he said. “You are actually going beyond language and have a better understanding of different ideas.”

    The findings were matched in a study of native Italian speakers who had learned English as a second language between the ages of two and thirty-four. Reading, writing, and comprehension were all tested. The results showed that the younger they started to learn, the better. “Studying a language means you get an entrance to another world,” explained the scientists.