题干

既可以用来鉴别乙烷和乙烯,又可以用来除去乙烷中混有的乙烯,得到纯净乙烷的方法是(   )

A:与足量溴反应

B:通入足量溴水中

C:在一定条件下通入H2

D:分别进行燃烧

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答案(点此获取答案解析)

B

同类题3

概要写作。阅读下面短文,根据其内容写一篇60词左右的内容概要。

    When a consumer finds that something he or she bought is faulty or in some other way does not live up to what the producer says for it, the first step is to present the warranty(保单),or any other records that might help, at the store of buying. In most cases, this action will produce results.

    However, if it does not, there are various means the consumer may use to gain satisfaction. A simple and common method used by many consumers is to complain directly to the store manager. In general, the “higher up” the consumer takes his or her complaint, the faster he or she can expect it to be settled. In such a case, it is usually settled in the consumer's favour, taking it as true that he or she has a just right.

    Consumers should complain in person whenever possible, but if they cannot get to the place of buying, it is acceptable to phone or write the complaint in a letter.

    Complaining is usually most effective when it is done politely but firmly, and especially when the consumer can show clearly what is wrong with what was bought in question. If this cannot be done, the consumer will succeed best by presenting specific information as to what is wrong, rather than by making general statements. For example, “The left speaker does not work at all and the sound coming out of the right one is unclear” is better than “This stereo(立体音响) does not work.”

    The store manager may advise the consumer to write to the producer, if so, the consumer should do this, stating the complaint as politely and as firmly as possible. But if a polite complaint does not achieve the expected result, the consumer can go a step further. He or she can threaten to take the seller to court or report the seller to a public organization responsible for protecting consumers' rights.

同类题4

阅读下文,回答问题

一条无野心的狼

       我家住在张广才岭下四面环山的山坳里。十岁那年春天的一天,我从山上采山菜回来,在山间小路旁边遇见一条骨瘦如柴、奄奄一息的小狗崽儿,我乐颠颠地抱回家养了起来,它身体很快恢复了,胖得圆乎乎的很是招人喜爱,整天跟在我的身前身后。看它毛色发青,就起名叫大青。

       一年后,大青长成了壮实剽悍的大狗,它非常仁义,从来不和别的狗咬仗,有时在院子里仰起头朝四处闻了一阵,便不知去向,回来时肚子吃得溜圆。说来奇怪,自从大青长大后,从前隔三差五不是这家猪崽被狼叼去了,就是那家小牛犊马驹让狼给咬死了,常常是每到太阳下山的时候,屯子的南山北岭便传来让人害怕的狼嚎声的现象再也没发生过。我家住在村子的副屯,上学需走二里地到正屯。善解人意的大青几乎是天天早晨把我送到村口,放学时它常常出其不意地在道旁的树丛中蹿出来,围着我连蹦带跳,有时还把两只前爪子搭在我肩上。春天我上山采山野菜有时害怕,我只要轻轻拍着它头,“大青别走,给我做伴儿”它就在我身前身后转悠从不离开。母亲常夸大青仁义、听话、通人性。

       雪后的一天,我的老舅,这里出名的炮手(猎手),进山打猎到我家歇脚。进院看见大青就喊着问:“姐,这是谁家的!”妈妈说:“是你外甥养的狗。”“姐,这不是狗,是条吃人的狼啊!”老舅吵嚷着。我放学回家,老舅板着面孔,十分严肃地对我吼道:“外甥。你养的不是狗,那是条吃人的狼!常言道,引狼入室后患无穷,让我把它处理掉吧?”我哭着对老舅说:“不是狼,它是我从小从山上捡回来的,可听话了,通人性,不能打死!……”老舅看拗不过我气得他连饭都没吃就走了。

       老舅生气走了,我急忙喊大青,喊了半天大青才蔫头耷脑地来了,身子紧紧贴着我,不进屋,也不吃食,眼睛总往四处瞅。就在这天晚上大青走了。我知道一定是老舅说的话,被大青听见了。我想大青想得睡不好觉,也吃不下饭,心事重重打不起精神来。

       六天后的晚上下了一场小雪,早晨我推开房门,在门旁有只冻硬的大公野鸡,我正心里纳闷儿,发现雪地上留下一趟狗的脚印,我明白了,这山鸡准是大青送来的。我喊来妈妈,妈妈看了后说:“大青这是报恩啊!”后来,每隔十天半月,大青在晚上不是悄悄送来山兔就是山鸡……一连三年,每到冬天落雪时大青都会送来它捕捉的一些小型野生动物……

       岁月悠悠,往事如烟,我与野狼大青这段感人往事,常常萦绕心头。它使我想起一句话:地球是人类与野生动物共同的家园。