题干

已知1.505×1023个X气体分子的质量为8g,则X气体的摩尔质量是(  )

C:64g/mol

A:16g

B:32g

D:32g/mol

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答案(点此获取答案解析)

D

同类题4

阅读下面的文字,完成文后题目。

鸟群

高亚平

    ①又是一个金风送爽的季节,我携妻带子回到了故乡。原野上,一丘丘成熟的水稻、苞谷、大豆散发出一种诱人的清香。农人们正在修车磨镰准备秋收,孩子们在乡场上玩耍,一群群的鸡在田畔渠头觅食。我望着眼前这些熟悉的场景,心里感到异常亲切。然而,于我的记忆中,似乎总少了一些什么,是什么呢?是鸟群。那种一到秋天,便一群一群的,于空中盘旋起落呼啸而过的鸟群。

    ②在我童稚的心灵里,在我少年无羁的记忆里,鸟群实在是一种令人陶醉的景观。

    ③我的家乡在樊川的腹地,它南依终南山,北靠少陵原,东傍一片丘陵,西依神禾原。川地中有无数的溪渠沟汊穿流其中。独特的地理环境,使这里水丰地肥,林木丰茂,是鸟类栖身觅食、繁衍生息的理想所在。记忆中,少年时代家乡的鸟似乎特别地多,房前屋后,水湄旷野,到处可见到鸟儿们飞翔的身影,觅食、嬉戏的踪迹。我家的门前是一道小溪,缘溪边生长着两排高大的树木,树木多为白杨、榆柳,也有一棵苦楝。树木的顶端有许多鸟窝,小巧玲珑的斑鸠窝,棕色硕大的喜鹊、铁老鸦窝,还有白鹤窝、黄鹂窝,以及一些不知名的鸟窝。至于燕子和麻雀,它们的窝多筑于人家的檐下屋内,树上找不到它们的巢穴。因了这个缘由,故而,我一年四季可以听到鸟儿们的鸣啼。

    ④春天,草木萌动,乡间便是一片欣欣向荣。“几处早莺争暖树,谁家新燕啄春泥”,燕子、大雁北迁,它们开始忙碌筑巢。杜鹃声声,黄莺乱啼,麻雀亦叽叽喳喳,让人觉出一片盎然的春意。我常常于酣眠中被窗外树木上的鸟鸣声惊醒,睁眼一看,外面已是一片明媚;阳光已越上了窗棂,爬上了树木梢顶。这时,我的心情便无限愉悦,穿衣、起床、吃饭。邀上小伙伴们,奔向原野上拔猪草,游玩嬉戏,找鸟窝,掏鸟蛋,或用自制的弹弓打鸟。鸟往往罹弹而殒,鸟蛋也往往被我们从树洞鸟窝中摸出,这些都被我们用湿泥裹了,放在火中烧透烤熟,洒上从家中偷出来的盐巴,分而食之。那种甘美、醇香,让我至今难忘。

    ⑤一首外国歌谣这样唱到:“夏日来了,令人回忆。”其实,令我回忆的鸟群,在家乡的夏日里是绝然看不见的。这并非鸟儿不多、不能成群的缘故,而是因为鸟儿们这个季节正忙于繁殖哺育后代;或者耐不得炎热,藏进绿树丛中。整个夏天,其实是鸟儿最多的时候,它们不扎群,亦不大鸣叫,只是在蓊蓊郁郁的树林里飞来飞去。只有到了傍晚,百鸟噪林的时候,你才可感到鸟儿的繁多,鸟群的庞大。一次,我和几位伙伴在树林中找蝉蜕,耐不得鸟儿的聒噪,我随手捡了一块石头,向树枝间使劲扔去。随着一声哀鸣,一只麻雀便若一片骤遭虫蛀霜打的树叶一样,从树枝间掉了下来。受惊的鸟儿“轰”地一声飞向天空,霎时间,鸣声一片,黑了头顶上的一片天空。

    ⑥然而,最让我痴迷的还是家乡秋天原野上的鸟群。

    ⑦几场秋风、几场秋雨之后,故乡的原野上便是一片金黄了。于丽日下,于澄明的碧空中,我们常常可以看见一道魅人的风景,那就是雁阵。大雁们排着“一”字形或“人”字形的队伍,嘎咕嘎咕地鸣叫着,从我们的头顶飞过,由北而南,渐去渐远,以至于无,令少年时代的我,生出无限的畅想。而呼啸的麻雀群,若风暴骤起于萍末,在庄稼地的上空,在乡场,刮来刮去,亦让人有一种惊心动魄的感觉。有时,麻雀群停驻在十几棵光秃秃的树上,树上便立刻像长满叶子。这些叶子在叫嚷着,吵闹着,让人觉出一种无限的生意。至于灰喜鹊,它们往往也在这个季节一大群一大群地从村庄的上空飞过,从原野上飞过,不知从哪里来,亦不知往哪里去了。还有一种鸟,我不知道叫什么名字,专门吃柿子。也是大群地来,每次来,家乡的柿子便会遭一次劫。但家乡人似乎并不恨这种鸟,有时在摘完柿子后,往往还给树上留下几个,供这些迟来的鸟儿们吃。

    ⑧曾几何时,家乡的鸟群在我们不知不觉间消失了。生态的破坏,环境的变迁,使河流干涸,树木减少,鸟群再也找不到一个可供栖身、生存的家园。现在,家乡广袤的原野上偶尔还能见到麻雀群。但在我看来,亦没有记忆中的庞大、壮观了。若干年后,连麻雀们是否也会弃我们远去?我说不清楚。社会在进步,人类在繁衍,但我们谁愿意面对一个没有鸟群的明天呢?站在故乡的土地上,我翻捡着少年时代的记忆,于心灵深处默默地呼唤:归来吧,我的鸟群!

同类题5

阅读理解

    Justin Bieber is only fifteen years old and has become very popular already. He was raised (抚养) by his mother in Stratford, Ontario, Canada. When he was twelve he won second place in a local singing contest. He started posting (贴) videos of his contest performances on the Internet for his friends and family. Soon these videos had been seen more than ten million times.

    A music manager saw those videos and asked Justin to fly to Atlanta, Georgia, to meet the singer and songwriter Usher. A year later Justin released (发行) his first albumMy World. It sold over a million copies in the first two months. Four singles were released before the album. All became popular. This made Justin Bieber the only singer in the history of the Billboard magazine to have four singles from his first album among the most popular songs before the album's release.

    Justin Bieber performed for President Obama at the White House last December. He was part of a musical show that raised money for the National Children's Medical Center. He was also among the many singers who recorded the song We Are the World. The song was produced to raise money for Haiti. The video has been seen more than seven million times on the Internet. And it was shown during the opening ceremony of the 2010 Winter Olympics in Vancouver.

    Justin Bieber's family did not have much money when he was young. He did not have as much so other children did. Justin says he wants to influence young people in a good way. He believes that you can do anything if you put your mind to it.