题干

某电镀厂的电镀液中含有金盐,为了回收其中的金元素,技术人员制作了如图的“吸金球”。“吸金球”是装入一些“吸金”物质的纱袋。把“吸金球”浸入电镀液,能“吸”出盐溶液中的金。据上所述,“吸金球”中的“吸金”物质可能是(          )

A:活性炭(C) 

B:磁石(主要成分是Fe3O4)

C:铁屑(Fe)  

D:胆矾(CuSO4.5H2O)

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答案(点此获取答案解析)

C

同类题2

阅读下面文章,完成相关问题。

冬眠的奥秘

张劲硕

       ①严寒的冬天,我们总是向往着在被窝里长眠一冬——能像狗熊和青蛙那样冬眠就好了。然而我们大都不知道:那些冬眠的动物们,掌握着我们人类尚不知晓的惊天奥秘。

       ②冬眠是动物应对恶劣环境的一种策略,科学上叫“蛰伏”。有人会问,冬天里睡得多、睡得久,不就是冬眠吗?它们还真不是一回事儿,只是二者的区别不太容易看出来。拿鱼来说,有几类鱼是会冬眠的,包括我们熟悉的鲤鱼、乌鳢,还有海里的鳗鲡。每当冬天来临,它们就把自己调到冬眠档:不吃、不喝、不游动。这看似与正常档的睡觉并无二致,但请注意它们的鳃!鱼类靠鳃呼吸,平时就算身体静止不动,鳃也会轻轻开合扇动。而进入冬眠的鱼,鳃也几乎不动,完全处于麻痹状态。除了呼吸,冬眠动物的体温、心跳等生命指征也都降到极低的水平,新陈代谢速率变得非常缓慢,与休克和死亡标准只差那么一点点——这就是冬眠与睡觉的本质区别。

       ③冬眠的意义在于,尽量减少身体内外的生命活动,将能量消耗降到最低,以挨过环境严酷的时间段。动物冬眠时,能把生命的时钟调得极慢。比如生活在北美洲的普通箱龟,冬眠时心脏5~10分钟才跳1次,实在让人惊叹。更夸张的是,它们几乎完全不呼吸,只靠皮肤吸入少许氧气!

       ④科学家还发现,冬眠不是“习惯养成”的问题,而是遗传基因决定的“天赋”。这种“天赋”还与寿命的长短有联系。一般来讲,哺乳动物的寿命与体型相关,体型小的新陈代谢快,寿命短;体型大的新陈代谢慢,寿命长。比如大象就活80年,兔子七八岁就算高寿。而蝙蝠打破了这个规律——冬眠的菊头蝠和同体型的、不冬眠的老鼠相比,前者可以活到30多岁,后者却只有3、4岁。如果在同一物种中比较,如蝙蝠或者棕熊,依然是冬眠的寿命要长很多。

       ⑤冬眠是当下的热门研究领域。如果人类能像动物们一样冬眠,收获的就绝不仅仅是睡大觉的幸福感,也许还能长生不老。虽然对蝙蝠和棕熊等冬眠动物的研究能确定冬眠基因与长寿有关。但这些动物毕竟与我们人类相差太远。不过,在2004年,有个轰动科学界的发现:居然有一种猴子能冬眠!而人类跟猴子同属灵长类动物,基因相似性很高。如果猴子能冬眠,这意味着我们人类也有可能做到。到那时,我们的寿命说不定可以达到800岁!

(选自《博物》总第146期,有删减)

同类题5

阅读短文,从每题所给选项中选出可以填入空白处的最佳选项,使短文完整正确。

    Will you put others' needs before your own? What 1 will you get if you do? Here is an experience of mine.

    It was a wet day and I had a 2time. I was busy and everyone I talked to was in a bad mood(心情). What's more, I went out without breakfast and I left my 3at home. So I couldn't get lunch and was terribly hungry.

    When I finished my work, I 4to ask my wife to meet me at the door with some money so that I could quickly go to buy 5. Then I quickly made my way home in hope of eating my 6meal of the day at 5:00 p.m.

    As I was halfway home, my wife told me by phone that a friend of ours was in 7and needed a lift(搭便车)home. My mind said, “I will get him 8I get the meal.” But my mouth said, “All right, I'll give him a 9

    He jumped in the car with a smile on his face and repeated how 10he was that I would drive him home. He told me he usually walked home from his company but that day the 11stopped him from making that journey.

    Traffic was 12. A drive to his home normally took 10 minutes, but that day it took 30 minutes.

    Now you would guess the person that I was helping is a 13friend of mine. But, in fact, he is a friend of a friend's.

    I wonder if I will ever see this person again, but I feel glad I was there when he 14me.

    So you will feel yourself helpful and useful when you 15more about others.