题目

下列有关实验现象的描述中，正确的是A.铁丝生锈后产生一种黑色固体B.红磷在氧气中燃烧时，生成大量白雾C.氯化氢和氨气混合产生白雾D.久置的未打磨的镁条表面呈深灰黑色 答案：【答案】D【解析】A、铁丝生锈后，产生一种红棕色固体，选项A错误；B、红磷在氧气中燃烧，产生大量的白烟，放出热量，而不是白雾，选项B错误；C、氯化氢和氨气混合产生成氯化铵，会观察到产生白烟，不是白雾，选项C错误；D、久置的未打磨的镁条表面有一层氧化物，呈深灰黑色，选项D正确。故阅读下面的短文，从短文后的选项中选出能填人空白处的最佳选项补全短文。选项中有一项为多余选项。Now the National Holiday is one of the biggest holidays in China.【1】When the National Holiday isThe National Holiday usually begins on October lst.【2】 If the Mid-Autumn Festival holiday falls within this period, the holiday period usually gets a day or two longer.The history of China's National DayOn October 1, 1949, Chairman Mao Zedong declared the founding of the People's Republic of China in Tian'anmen Square. The next day, the new government passed the "Resolution on the National Day of the People's Republic of China" and declared October 1 to be the Chinese National Day.【3】National Day celebrations/activitiesNow every 5 years, a military parade(阅兵)is held in Tian'anmen Square. Those great military parades have attracted a lot of people from both home and abroad.【4】If one loves shopping, the National Day holidays is a great time, for many shopping centers offer big discounts during the holiday.A.Ever since then, our National Day has been on October 1 every year.B.During the golden week, lots of Chinese people go traveling.C.It lasts till October 7.D.Other activities like flag— raising ceremonies, song and dance shows, and firework displays are also held to celebrate National Day.E.At this time, we have a week off to stay with our family or go on trips.