题干

 关于声现象,下列说法正确的是

A:二胡演奏出的优美旋律,是由弦的振动产生的

B:运动员打鼓用的力越大,鼓声的音调就越高

C:女航天员王亚平在天宫一号上讲课的声音是通过声波传回地球的

D:“禁止鸣笛”是在传播过程中减弱噪声

上一题 下一题 0.0难度 选择题 更新时间:2015-07-07 05:19:21

答案(点此获取答案解析)

A

同类题2

阅读下面的文字,完成下列小题。

一棵树的故事

王建平

    原本,那棵树的故事已有了句号,哪想,今春一个议题,让树的话题得以延续。

    春节刚过完,西村村长陪县减灾办的科技人员上山来,对有隐患的山体进行一番考察后,拟定一个议题:全村唯有村民刘有福的房反紧贴着松酥山体,此处属泥石流重大隐患区,入夏前必须搬下山。

    此事一嘈开,都说刘有福命好,要住政府出钱修建的新房了,真是有福。哪料,风声吹进刘有福的耳朵里,他心烦意乱,嘴与老屋的门一下紧闭起来。心想,住山上五六十个年头,那坡那梁那路那草那花那田那地的样儿全烙在心中,我跟它们知根知底知深知浅知冷知暖的日子数不清.哪舍得离开呀?

    这天朝阳照亮山梁,刘有福开门晒太阳,门一开就跟门外的人照上面。见村长第九次上门来,刘有福一下蹲地上,勾下头。

    村长说,五叔,这山上真的那么好吗,山高路难行,这些年夏天的暴雨季节夜里,你和五娘做过一个完整的梦没?

    刘有福没出声,他咋会不知山洪的冲击声跟雷声搅在一起,夜里可吓死人了,他和老伴常常缩在墙角听天由命……老伴去年病故……想到这儿,他抬头吭了一声。

    今的老房子搬下山?

    肯定的。村长应。

    我的鸡鸭猪狗牛全下山?刘有福又问。

    那是必须的。村长应。

    那……我的这棵树?刘有福迟疑一下,吸入一口气,吐完后半句,我的树也要下山!

    当……当然……村长仿佛没想好就从嘴里遛出了几个字。瞬时,他才明白老人家的愿望。老人家的那棵树太大太粗了,要搬下山的确不是一件易事。

    刘有福老屋前有一颗黄桷树。

    七十年前的一个冬天,刘有福二十多岁的爹,趁一个风雪夜看守将不严,从壮丁集中营逃出来,路遇一位砍柴人便讨得一根树枝,好几天粒米未进,靠喝冬水田里的水和手上的树枝拄回家。到家后他爹在门前用锄头挖下一个坑,栽下了树枝。没想到呀,七十多个春夏秋冬过去,树——悬跟露爪,树干粗壮得两人合围。树体歪针,长相怪异,主枝横伸树冠宽阔,枝繁叶茂。刘有福常想.树是爹,爹是树,这么些年有爹陪伴心里总是满满的。

    住西村山脚下的二宝,四十岁不到,闯荡过好几个省,是村里村外的大能人。二宝每次来见刘有福,嘴皮子热乎极了。二宝第三次上山,五叔前五叔后贴住刘有福的屁股转。

    五叔,二宝向刘有福敬上带把儿的烟。我想好了,愿出3000元买你的这棵树。

    叭——刘有福将一口痰射击出两米多远。

    3500元呢?二宝脸上堆积着笑。

    刘有福的目光移向树.眼晴不动了。那树.古态盎然.叶片儿油绿光亮,有数不清叫不出名字的鸟儿正左树上嬉戏,它们不离开树,爱恋着老屋散发出的古老气息,更没嫌弃过刘有福和他鸡鸭猪狗牛们身上传递给它们怪怪的酸味……刘有福眼晴湿了。

    五叔,5000元怎么样?二宝加价。

    刘有福手中烟锅嘴儿在地上敲了敲,起身扛起一头白发迈向老屋。二宝没想到,他五叔在门口突然转过身来,说,侄儿——你能,我出钱,请你把树移下山吧!

    三个月过去,刘有福在山下的新屋建好了。树在昨天也由二宝移下山,在新屋门前栽好。刘有福牵着牛在草地吃草,他远远地望着新栽下的树干,入神了,连二宝的侄儿小强来到自己面前也没察觉。

    五爷,二叔是真心想得你的树,活树没到手,等树死了,他还要来买。小强对看刘有福的耳朵说。

    嗯?刘有福回头盯住小强。

    二叔说树的根部可以打造成根雕茶几,树干和粗枝可雕刻成上百件工艺品,他已访好了买家,那人报价58000元。

    树会死?刘有福眼晴闪烁一下。

    会的,树下坑的头天晚上,二叔在后半夜往坑底的泥土里理了生石灰。小强接着说,化学课学过,生石灰被水泡散了就成了石灰水,石灰水具有强碱性,会烧死树根的……

    夏去秋来,刘有福的树发出的新芽变成了嫩绿的小叶儿。

    幸好那晚刘有福请人与小强从树千侧面挖出一个深坑,从树根下构出好几块生石灰,换上了新土。树呀,你命大,二宝埋下去的生石灰还没化开,要不……

    刘有福独自来到镇上的学校,他为并不沾亲带故的孙子小强交了5000元的生活费。面对老师的询问,刘有福说,谢老师啦,那娃儿的书没白读!

同类题4

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Some years ago, writing in my diary used to be a usual activity.I would return from school and spend the expected half hour recording the day'sevents, feelings, and impressions in my little blue diary. I did not reallyneed to express my emotions by way of words, but I gained a certainsatisfaction from seeing my experiences forever recorded on paper. After all,isn't accumulating memories a way of preserving the past?

When I was thirteen years old, I went on a long journey on footin a great valley, well equipped with pens, a diary, and a camera. During thetrip, I was busy recording every incident, name and place I came across. I feltproud to be spending my time productively, dutifully preserving for futuregenerations a detailed description of my travels. On my last night there, Iwandered out of my tent, diary in hand. The sky was clear and lit by the glareof the moon, and the walls of the valley looked threatening behind their screenof shadows. I automatically took out my pen...

At that point, I understood that nothing I wrote could evermatch or replace the few seconds I allowed myself to experience the dramaticbeauty of the valley. All I remembered of the previous few days were the dullcharacterizations I had set down in my diary.

Now, I only write in my diary when I need to write down aspecial thought or feeling. I still love to record ideas and quotations thatstrike me in books, or observations that are particularly meaningful. I takepictures, but not very often only of objects I find really beautiful. I'm nolonger blindly satisfied with having something to remember when I grow old. Irealize that life will simply pass me by if I stay behind the camera, busypreserving the present so as to live it in the future.

I don't want to wake up one day and have nothing but a pile ofpictures and notes. Maybe I won't have as many exact representations of peopleand places; maybe I'll forget certain facts, but at least the experiences willalways remain inside me. I don't live to make memories--I just live, and thememories form themselves.