题干

往无色溶液中滴加氯化钡溶液产生不溶于稀硝酸的白色沉淀,则该无色溶液中(  )

A:一定含有硫酸根离子

B:一定含有银离子

C:只有硫酸根离子,没有银离子

D:可能含有硫酸根离子或银离子

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答案(点此获取答案解析)

D

同类题2

短文赏析

老驼的喘息

梁晓声

    ①我这个出生在哈尔滨市的人,下乡之前没见到过真的骆驼,便是骆驼的活动影像也没见过。

    ②直到落户北京的第一年,去了一次动物园,我才见到了真的骆驼。数匹,有卧着的,有站着的,极安静极闲适的样子,像是有驼峰的巨大的羊。肥倒是挺肥的,却分明被养懒了,峰向一边软塌塌地歪着,未必仍具有在烈日炎炎之下不饮不食还能够长途跋涉的毅忍精神和耐力了。那一见之下,我对“沙漠之舟”的敬意和神秘感荡然无存。

    ③后来我到新疆出差,乘吉普车从戈壁驶近沙漠地带时,又见到了骆驼。

    ④那是秋末冬初时节,当地气候已冷,夕阳西下,大如轮,红似血,三匹骆驼屹立风中,从十几米外望着我们。它们颈下的毛很长,如美髯,在风中飘扬。它们的峰很挺,皆瘦,都昂着头,姿态镇定,使我觉得眼神里有种高傲劲儿,介于牛马和狮虎之间的一种眼神。

    ⑤陪行者说,这三头骆驼很可能曾是家驼。主人原本是靠它们驮运货物来谋生的,自从汽车运输普及后,骆驼的用途渐渐过时,主人继续养就赔钱了,可又不忍杀它们,于是骑到离家远的地方,趁它们不注意,搭上汽车走了。骆驼的记忆力很强,是完全可以回到主人家的;但骆驼又是有自尊的,意识到自己被抛弃了,宁肯渴死饿死冻死,也不会重返主人的家园。然而它们又对人养成了一种信任心,即使成了野骆驼,见了人,还是挺亲的。

    ⑥那一次在野外近距离见到了骆驼以后,我才真的对它们心怀敬意了。

    ⑦不久前,我在内蒙古的一处景点旅游,骑到了一头骆驼背上。那景点养有一百多头骆驼,专供游人骑着过把瘾。但须一头连一头,连成一长串,集体行动。

    ⑧驼队行进在波浪般起伏的沙地间,我忽然感觉有东西拱我的肩,勉强侧身一看,是我后边的骆驼翻着肥唇,张大着嘴。我怕它咬我,只得尽量向前俯身,但却无济于事。骆驼的脖子那么长,它的嘴仍能轻而易举地拱到我。有几次,我感觉到它柔软的唇贴在了我的脖梗上,甚至感觉到它那排坚硬的大牙也碰着我的脖梗了。

    ⑨倏忽间我于害怕中明白——它是渴了,它要喝水。而我,一手扶鞍,另一只手举着一瓶还没拧开盖的饮料。我当然是乐意给它喝的,可我不敢放开扶鞍的手,而且就算我能拧开瓶盖,也还是没法将饮料倒进它嘴里,我有严重的颈椎病,扭身对我是件困难的事。

    ⑩它却不拱我了。我背后竟响起了喘息之声。那骆驼的喘息,类人的喘息,如同负重的老汉紧跟在我身后。我一向以为,牛啦,马啦,骡啦,驴啦,包括驼和象,它们不论干多么劳累的活都是不会喘息的。那一天那一时刻,我才终于知道我以前是大错特错了。

    ⑪既然骆驼累了是会喘息的,那么一切受我们人所役使的牲畜或动物肯定也会的,只不过我以前从未听到过罢了。

    ⑫那骆驼不但喘息,而且还咳嗽了,一种类人的咳嗽,又渴又累的一个老汉似的咳嗽。举着一瓶饮料的我,生平又第一次听到骆驼的咳嗽声……

    ⑬一到终点,我立刻拧开瓶盖要使那头骆驼喝到饮料。偏巧这时管骆驼队的小伙子走来,阻止了我。因为我手中拿的是一瓶葡萄汁,骆驼是不能喝果汁型饮料的。

    ⑭我问他这头骆驼为什么又喘又咳嗽的。他说它老了。我说:“既然老了,那就让它养老吧,还非指望这么一头老骆驼每天挣一份钱啊?”小伙子说,驼群每天都集体行动,单将它关在圈里,它会感到受了侮辱,它会郁闷的,不久就容易病倒的。

    ⑮我无话可说了。那老驼尚未卧下,一动不动地站在原处,瞪着双眼睇视我,说不清望的究竟是我,还是我手中的饮料。我经不住它那种望,转身便走。   

    ⑯几个月过去了,我耳畔仍每每听到那头老驼的喘息和咳嗽,眼前也每每浮现它嗔视我的样子。

同类题5

阅读理解

    A new American weather satellite could save more lives by better predicting extreme weather conditions. It will be in orbit(轨道)some 36,000 kilometers above Earth's surface. The National Oceanic and Atmospheric Administration, also known as NOAA, has been working with the National Aeronautics and Space Administration (NASA) on the project.

    NOAA officials are calling the new satellite GOES-R. That is short for a much longer name—the Geostationary Operational Environmental Satellite-R Series. NOAA said GOES-R could improve the nation's ability to observe weather conditions and make weather predictions. It said the satellite's operation would lead to more exact and timely weather forecasts watches and warnings.

    The government agency said the satellite will require testing of its six instruments and will be ready to work “within a year."

    "The next generation of weather satellites is finally here." said NOAA Administrator Kathryn Sullivan. She described GOES-R as one of the most complicated Earth-observing machines ever created. Sullivan said its instruments will be able to study Earth five times faster and with four times more detail than any other NOAA satellite currently in operation. She believes this will make the United States an even stronger, more “Weather-Ready" nation.

    A NOAA statement said the greater detail will help improve the agency's study of ocean storms, as well as “the prediction and warnings of severe weather. "In addition, GOES-R will be able to provide improved rainfall estimates (预计), which will lead to more timely and detailed flood warning. The statement also said that GOES-R will give better estimates of wind strength, as well as better measurement of fog, ice or lightning strikes.

    Craig Fugate serves as administrator of the Federal Emergency Management Agency. He says that the GOES-R satellite will improve the ability of people and organizations across America to prepare for, and react to, weather-related disasters.