题干

常在某些建筑材料中添加阻燃剂以防止火灾。Mg(OH)2是一种常见的阻燃剂,在380℃时分解成水蒸气和MgO。下列说法正确的是()

A:Mg(OH)2属于混合物

B:MgO属于氧化物

C:Mg(OH)2能降低可燃物的着火点

D:MgO中两元素的质量比为1:1

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答案(点此获取答案解析)

B

同类题2

阅读下面文言文,回答相关问题

                                                                                    【甲】
      ⑴余幼时即嗜学。家贫,无从致书以观,每假借于藏书之家,手自笔录,计日以还。天大寒,砚冰坚,手指不可屈伸,弗之怠。录毕,走送之,不敢稍逾约。……
      ⑵今诸生学于太学,县官日有禀销之供,父母岁有裘葛之遗,无冻馁之患矣;坐大厦之下而诵《诗》《书》,无奔走之劳矣;有司业、博士为之师,未有问而不告,求而不得者也;凡所宜有之书皆集于此,不必若余之手录,假诸人而后见也。其业有不精,德有不成者,非天质之卑,则心不若余之专耳,岂他人之过哉?……
      ⑶自谓少时用心于学甚劳,是可谓善学者矣!其将归见其亲也,余故道为学之难以告之。
                                                                                                                                                      ——(宋濂《送东阳马生序》节选)
                                                                                     【乙】
      临川之城东,有地隐然而高,以临于溪,曰新城。新城之上,有池洼然而方以长,曰王羲之之墨池者。荀伯子《临川记》云也。羲之尝慕张芝,临池学书,池水尽黑,此为其故迹,岂信然邪?方羲之之不可强①以仕,而尝极东方,出沧海,以娱其意于山水之间。岂其徜徉肆恣②,而又尝自休于此邪?则其所能,盖亦以精力自致者,非天成也。然后世未有能及者,岂其学不如彼邪?则学固岂可以少哉!况欲深造道德者邪?
                                                                                                                                                              ——(曾巩《墨池记》节选)
【注释】①强:勉强   ②徜徉(chángyáng)肆恣:纵情遨游。

同类题4

 Are you a happy person most of the time? Or do you easily get angry sometimes? Everyone has a different temperament (脾气). It is usually believed that both genes (基因) and environment may affect people's temperaments in different ways. But now scientists have found that the season of birth also plays a role.

 Scientists from Budapest, Hungary, studied 400 university students. In the study, the students needed to finish a questionnaire (问卷). The purpose of it was to find out which of four kinds of temperaments they most had. From the questionnaire, scientists found that the students always answered something like "My mood often changes for no reason" and "I love to deal with new projects, even if it is risky". These answers were then matched with their birthdays.

  They discovered that people born in summer easily change between sad and happy moods compared to people born in winter. Those who always feel positive are mostly born in spring and summer.

The study also found that those born in autumn less probably had a mood of depression which may easily drive them to cry, while those born in winter were not easier to be angry.

 Scientists said that this was probably because the seasons had an influence on certain chemicals in the human body. And the chemicals are important to control people's moods even in adult life.

  ____________________________________________________________________________

"It seems that when you are born may increase or decrease your chance of developing certain mood disorders (紊乱)," lead scientist Xenia Gonda told The Telegraph.