题干

两支内径粗细不同、下端玻璃泡水银量相等的合格温度计,同时插入同一杯热水中,水银柱上升的高度和温度示数分别是(   )

A:上升高度一样,示数相等

B:内径细的升得高,它的示数亦大

C:内径粗的升得低,但两支温度计的示数相同

D:内径粗的升得高,示数也大

上一题 下一题 0.0难度 选择题 更新时间:2019-03-22 05:09:27

答案(点此获取答案解析)

C

同类题2

阅读理解

     The World Meat Free Day for 2017 falls on 12, June, but what would actually happen if the whole world suddenly went vegetarian(素食的) permanently?

     If vegetarianism were accepted by everyone by 2050, the world would have about seven million fewer deaths every year. No meat would lower the chances of some diseases or even some cancers and so save the world 2-3% global GDP in medical bills. Food-related emissions would drop by around 60%. This would be due to getting rid of red meat which come from methane (甲烷) producing livestock (家畜) — from people's diets. Turning former pastures (牧场) into native habitats and forests would slow climate change and bring back lost biodiversity, including some animals which were previously pushed out or killed in order to keep cattle.

    However, farmers in the developing world could really suffer. Arid and semi-arid lands can only be used to raise animals as there's no or little water in these places, such as the Sahel land strip in Africa next to the Sahara; nomadic (游牧的) groups that keep livestock there would be forced to settle permanently and lose their cultural identities if there were no more meat. Losing meat also means that we also lose traditions. There's no more Christmas turkey. We would need to replace meat with nutritional substitutes, in particular for the world's estimated two billion-plus unhealthy or weak people for lack of nutrients. Animal products contain more nutrients per calorie than staples like grains and rice.

    Everybody currently engaged in the livestock industry would need to be retrained for a new career. This could be in agriculture, reforestation or producing bioenergy. Failing to provide career alternatives could lead to mass unemployment and social problems, particularly in traditionally rural communities.

同类题4

阅读《不可小觑的镉大米与镉中毒》,完成下列各题。

不可小觑的镉大米与镉中毒

       ①近期,湖南大米因含镉量超标再次成为全国公众关注的焦点。“镉大米”危机瞬间席卷全国,各地纷纷抽检自查,结果令人震惊:全国约有10%的大米镉超标。

       ②“镉大米”,指镉含量超标的大米。镉和大米的渊源很深,水稻很容易吸附镉。镉主要与锌矿、铅锌矿、铜铅锌矿等共生。在开采这些矿时,含镉工业废气扩散并自然沉降,蓄集于周围土壤中。即使距离较远,其排放的废气扩散后,也可能随降雨落入农田,污染粮食。镉也存在于一些化学肥料中,特别是磷肥中含量较大。如果过度使用磷肥,植物无法全部吸收消化,镉就会吸附到大米当中去。我国磷肥中镉的含量约在0.1﹣2.9mg/kg,而美国为7.4﹣15.6mg/kg,澳大利亚则为18﹣91mg/kg。正常施用中国磷肥对土壤镉超标的影响很小,但是中国的优质磷被出口,而进口国外的劣质磷,导致中国土壤中的镉含量升高,从而产出镉大米。灌溉水污染是最具威胁的一种,其杀伤范围和力度都非同小可。从地下挖出来的矿砂没有得到妥善的处理,遇到雨水,矿砂中的镉会随着雨水游走,污染了水源。用污染水灌溉农田,镉就会通过土壤进入粮食作物。

       ③镉进入人体后,主要蓄积于肾脏,对肾脏造成损害,抑制维生素D的活性。维生素D是人体不可缺少的营养素。缺乏维生素D会妨碍钙、磷在人体骨质中的正常沉着和储存,最后导致骨软化。人吃了含镉的食物不会马上有感觉,根据科学家批露,镉一般在几十年以后对身体造成影响,特别是身体会有莫名其妙的疼痛等症状,这就是镉造成的后果。

       ④普通百姓虽然无法从肉眼上识别哪种大米镉超标,但只要购买大米时,多选择不同产地、不同品牌的稻米品种就可减少镉中毒。同时提倡膳食多样化,尤其是以大米为主食的南方居民,适当增加主食品种以降低风险。另外,多吃海产品、豆类等含锌、钙量较高的食品,都可以降低人体对镉过量摄入而患病的风险。

(根据有关材料改编)