题干

下列物质分子中一定含有π键的是

A:HCl

B:H2O2

C:C2H4

D:CH2Cl2

上一题 下一题 0.0难度 选择题 更新时间:2017-03-02 10:21:46

答案(点此获取答案解析)

C

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    Five meteorologists (气象学家) who were trapped for two weeks after polar bears surrounded their weather station are now able to leave after the creatures were chased away. Their supervisor told NBC News early Wednesday.

    Russian officials had feared the siege could last for another month, the time it would take to reach the islands in the Kara Sea, high in the Arctic Circle. But on Tuesday night a research ship took a detour (绕道) to assist those weathermen, station supervisor Vasily Shevchenko told NBC News. The ship run by Russia's state-run oil firm Rosneft frightened away the bears using its helicopter, before resupplying the weather station with more food and puppies (幼犬) . The puppies are not yet big enough to deter the bears, but the station is planning to draft in a replacement adult guard dog as soon as possible.

    Some of the bears had taken to sleeping directly outside the windows of remote outpost. There was no risk of the researchers starving because they had a year's worth of food, but they were forced to take dangerous trips to a nearby building, holding a gun for protection, according to Shevchenko.

    Polar bears are an endangered species. In Russia, it's a crime to shoot them unless in self-defense. The bears usually leave the islands in the summer, but this time they were trapped by the melting ice, an apparent sign of climate change, according to Shevchenko. “They've stayed on the island because there is nowhere for them to go,” he said.

    The animals suffer from global warming because it shrinks the floating ice that forms their main hunting ground. According to the environmental group the World Wide Fund for Nature, known as the WWF, this has got some polar bears to go near human habitats in search of food.

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                                                                                                                                    你在伞里吗

        ①雨渐渐大起来。后座上的女儿,小脸紧贴着我的后背,右手穿过我的胳肢窝,擎着她那把橘红的小伞。雨砸在伞顶上,嘭嘭直响。有风,车子骑得有些吃力,那小伞也忽嗒忽嗒不甚听话,但女儿努力地擎着它,我能感觉到她的小手在我的腋窝下一次又一次用力。我问道:“你在伞里吗?”

        ②“妈妈,在!”女儿的回答响亮而干脆,那语气里的阳光,穿过这晦暗的雨幕感染着我的心。女儿今天是太高兴了——期中考试,她语文.数学都得了一百分,按照考前的承诺,我要请她吃一顿肯德基。

        ③女儿左手攥着的纸袋里,此刻就装着她小小的愿望,热乎乎的,与她热乎乎的小脸一起紧贴着我的后背。车子一颠一颠,女儿的小脸和那纸袋与我的背脊若即若离,那温暖也就一阵一阵——可就是这一阵一阵的温暖,让我寒雨里的心一阵阵颤栗!

        ④肯德基的店铺在这个城市里随处可见,但我的女儿对肯德基却一直保持着向往与好奇。去年她9岁生日那天,我第一次带她去肯德基,她用薯条蘸着番茄酱,放进嘴里小心翼翼地嚼,那满足的眼神让我几乎不敢面对……为了自己的梦想,我辞职来到这座城市快两年了,我不得不节约血汗换来的每一分钱,以应付房租.伙食费以及女儿不菲的借读费。小小的女儿,便也常常受我所累,有时一些小小的愿望都难以实现……

        ⑤雨没停,风也没停,而我们离租住的小屋还很远。我把胳肢窝里的女儿的小手夹得紧一些,想让她省些力气。与此同时,我又问了一遍:“你在伞里吗?”女儿的回答还是那一声响亮而干脆的“在”!

        ⑥到家了,我用腿撑着车,腾出左手抓住伞柄,好让女儿抽出手来。当我转过脸的刹那,我呆住了——女儿几乎全身湿透!但她微笑着,扯了扯我的上衣,又拍拍那个纸袋,紧紧地抱在胸前:“它没湿,还热着呢!”

        ⑦泪水和着雨水,从我的脸上流淌下来一瞬间打湿了我的脸……