题干

下列事实不能用胶体的知识来解释的是

A:用某些含铝的化合物作净水剂

B:医学上利用用透析的手段净化尿毒症患者的血液

C:用一束平行光线照射蛋白质溶液时,从侧面看可看到光亮的通路

D:向FeCl3溶液中滴入NaOH溶液,出现红褐色沉淀

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答案(点此获取答案解析)

D

同类题2

阅读理解

    For the first time in the history of the Beijing, Shanghai and Hangzhou marathons, fourteen blind runners competed in the Nov 6 Hangzhou Marathon this year with the assistance of personal guides. Each runner was supported by 4 or 5 volunteers. Among them was Yan Wei, from a running group called “Running in the Dark”, which specially provides training for blind runners.

    During trainings, blind runners are each accompanied by three volunteers. One volunteer is responsible for removing any obstacles(障碍物)on the road and controlling the pace. The second volunteer acts as a lookout for other runners or vehicles on the path while the third, who is attached to the blind runner by a safety rope, takes note of the trainee's running gait and pace.

    Zhu Peihua, the leader of the group's Shanghai branch, first developed a passion for running last year when he took part in a guided running activity. Zhu said that he was so fascinated with the sport that he even bought a treadmill(跑步机)so that he could train at home. “Running gives me the chance to be outside and take in the fresh air. The activity has also made me more willing to talk to people. It's simply good for health, ” said Zhu.

    The popularity of guided running activities for blind people has been growing since last year. Cheng Yi, a volunteer at Running in the Dark's Hangzhou branch, said that both the numbers of blind runners and volunteers to become assistants to them are rising continually. However, he added that volunteers face a more physically demanding task compared to a regular runner. Some of the other challenges involve being aware of the verbal(口头的) instructions one gives.

     “At the beginning, I kept saying ‘here' and ‘there' instead of ‘left' or 'right' which is much more specific and relevant to the runner. A blind runner once collided with another runner because of my mistake. Luckily, no one was hurt,” said Cheng. Through everything, according to Cheng, he and many of the blind runners he has guided become close friends with shared topics and increased understandings.

同类题5

阅读下面的文章,完成后面的题目。

麦香

叶青才

    这是人间四月天,这是草莓吐出酸酸甜甜气息的流翠时节。

    我回乡看望一位老人,一位老了还能闻见麦香的庄稼人。

    他是我的尊长,也是最关心我的人之一;他是那块麦地的主人,同时也是一棵熬过冬天的麦子

    我径直到他的麦地里,就像熟悉那棵苦丁茶那样,一眼就看见了他。我好久没有置身麦地了,好久没有闻见过这么浓郁的麦香。这味儿像槐花里掺进了蜜,像玫瑰里拌入了糖,还有点淡酒的余味。是的,麦粒成熟之后,渗入点水,发胀,抽芽,便是熬糖做酒的原料了。然而现在麦子正青,才抽穗扬花,这只能是麦花香。

    在麦花香里,我细细打量着这位教我割麦的人。他满头银丝,胡须也渐白了。身子骨似乎依然坚实,只是笑起来,没有了管风的牙,没有了细细的皱纹。他的纹路粗了,深了,长了,像地边的沟道,纵横牵连,总想寻个出处奔去。人一老,这沟道就流淌着岁月的回声,你没法将它阻住,也没法把它拽回。我想到我不要多久也会是这个样子,岁月的回声满耳,光阴的脚步匆匆,我会停留在哪一截道上呢,抑或在哪一块地边呢?

    他已经不是我印象中的荣伯了。你看他劳作的姿势虽然保留了过去一直有的那种利索和老到,但是明显力度不够,虚实交杂中虚的成分多了。剪除枯老的茶株,砍掉高高的茶桩,这样的活儿要是搁在前几年,荣伯是一抹不挡手的。他眼疾手快,手到心到,剪出的新茶棵像刚刚修剪的平头,齐崭崭,平覆覆,精神抖擞地立在麦地边上,衬托出四月特有的生机和活力。眼下,他似乎不愿在我面前显老,他动作的幅度很大却藏不住虚张的声势,吃力而现出连贯的破绽。那些他亲手种出的麦子,倒是一片青葱,仿佛荣伯的青春都让麦子给偷盗去了,这种活力与肤色的转移,直让我觉得一个人原来也不过是一棵麦子,一棵曾经锋芒毕露的麦子,走过了嗞嗞拔节的日子,走过了飞絮扬花的岁月,随后就走进了他枯萎与衰残的暮年。

在乡下时,我也收割过麦子,并且手指被麦秸秆割破,眼睛被麦芒刺中,我却在那种潜在的伤害中闻到了麦香,那股成熟的带着馒头和挂面香味的气息,它一点点渗透到我的鼻孔里、肺腑里乃至梦幻里,而我青涩的汗味和冒冒失失的语言气息,反倒自个儿一点都不觉察,只有身边的大人,比如荣伯,才准确地把住了我突突的腕脉,并且通过镰刀和锄头将我那些蒲公英一般的欲念摁下去,让我接近麦茬和犁头草,接近土地上最切实的部分。现在想来,麦花香里那些醉人的芬芳和诱人的味道都不过是四月天落下的槐荚与桑椹,它们其实结不了什么果实,虽然不乏甘甜,却只能徒增味觉的依赖和幻觉的空乏。

    真正的麦香总是与镰刀在一起,与即将到来的梅雨在一起不久,荣伯新剪的茶棵又将长出青幽幽的茶叶来,把大片萎黄的麦子衬托得分外衰老。然而,整个村子在这时才激动起来,就像荣伯在黎明俯身于麦地一样,天空晴朗而高远,大地芬芳而宽阔。当青春的梦幻醒来,我发现,一个距离大地最近的人就是一把镰刀或扁担,一声动情的呼喝就是一阵麦浪或槐风。时节正值端午,太阳正在背脊之上,村庄正在麦香之中,而我正在麦粒之外。

    那时,成熟的麦子香气四溢,倘若旁边有梅子,它会落入梅香;旁边有李子,它会融进李馥。

    熟麦的香味曾经把我的乡居整个地淹没了。荣伯揉开一穗麦朵,在掌心,他细细地吹掉麦芒和麦壳,让一堆鼓胀的新麦裸露在五月的太阳下。他拈起其中一粒,放入嘴里,然后嚼起来,这时候,我看见天空蓝得有些承受不住,而荣伯眯缝的眼睛却成了两穴幸福的陷阱。

    一个能被麦香陶醉的人,他的幸福简单得很,也悠远得很,他的祝愿有时就是他的遗憾,他的挽留同时也是他在送行。他不知道有很多东西都是留不住的,像滑溜的时光、逃跑的庄稼以及跟欲望一起私奔的人,像他手把手教了16年割麦技术的那个瘦小的身影,到底还是在五月的麦芒直视下溜之大吉……

    一转眼30年,时光快得就如一地麦子从四月走进五月,从花香进入谷香。

    老了的荣伯面对我的到来,只能欢喜地连声说:你回来了,回来了!你看今年的麦子……他哪里知道,我原本就没打算看望这一地青青麦子,我不过是在麦地里寻找他罢了,就像那年我回去寻找当年我爬过的一棵青桐树,结果却找到了一条我从来没有放在心上的幽幽小路。

    是麦香帮了我的忙,让我找回了镰刀与麦茬旁边的自己,还有这位将庆幸和失望发酵在一起的荣伯。                       (选自《散文百家》2014年第2期)