题干

炼铁高炉中发生了下列反应:①高温下一氧化碳将铁矿石还原为铁  ②高温煅烧石灰石 ③灼热的焦炭和二氧化碳反应    ④焦炭充分燃烧

其中属于化合反应的是(  )

A:①和④

B:②和③

C:③和④

D:只有④

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答案(点此获取答案解析)

C

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    Owning a smartphone may not be as smart as you think. It may let you surf the Internet, listen to music and snap photos wherever you are…but it also turns you into a workaholic, it seems.

    A study suggests that, by giving you access to emails at all times, the all-singing, all-dancing mobile phone adds as much as two hours to your working day. Researchers found that Britons work an additional 460 hours a year on average as they are able to respond to emails on their mobiles.

    The study by technology retailer Pixmania reveals the average UK working day is between 9 and 10 hours, but a further two hours is spent responding to or sending work emails, or making work calls. More than 90 percent of office workers have email-enabled phones, with a third accessing them more than 20 times a day. Almost one in ten admits spending up to three hours outside their normal working day checking work emails. Some workers confess(承认) they are on call almost 24 hours a day, with nine out of ten saying they make work emails and calls outside their normal working hours. The average time for first checking emails is between 6 a.m. and 7 a.m., with more than a third checking their first emails in this period, and a quarter checking them between 11 p.m. and midnight.

    Ghadi Hobeika, marketing director of Pixmania, said, “The ability to access literally millions of apps, keep in contact via social networks and take photos and video as well as text and call has made smartphones invaluable for many people. However, there are drawbacks. Many companies expect their employees to be on call 24 hours a day, seven days a week, and smartphones mean that people literally cannot get away from work. The more constantly in contact we become , the more is expected of us in a work capacity(容量).”