题干

电影《黄金大劫案》上映后,里面用“王水”(浓盐酸与浓硝酸的混合液)溶解黄金的情形起了广泛的热议.黄金溶解在“王水”中形成HAuCl4(四氯合金酸),没有氢气产生.根据以上信息,下列有关说法正确的是(   )

①“王水”溶解黄金是化学变化;

②金比氢活泼;

③HAuCl4中,Au的化合价为+3价;

④可以将pH试纸伸入“王水”中测其酸碱度;

⑤“王水”可以用铁质容器盛装.

A:①④⑤

B:①③

C:③④⑤

D:①②③

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B

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    If you like texting and are trying to lose weight, a new study found that using texting(发短信) to track diet and exercise habits may help you lose weight.

    Previous research has shown that keeping food and exercise diaries improves the likelihood of success when you are using it to lose weight. Using a computer or a pen and paper to record information, however, can be a burden and cause some people to give up.

    Duke University researchers said using text messages to track eating and exercise habits can save time, and increase the chances that people will stick with their weight-loss rules.

    The study included 26 obese/fat women with an average age of 38. The women used daily texting as part of their weight-loss program. The text messages focused on tracking personalized goals, such as avoiding sugary drinks or walking 10,000 steps a day. Messages also provided brief feedback (反馈) and tips.

    Every morning, the women received a text from an automated system that said, “Please text yesterday's personal information of steps you walked and how many sugary drinks you had.” Based on the women's responses to the text message, the system sent another text with personalized feedback and tips.

    After six months, the women who used daily texting lost an average of nearly 3 pounds, while another group of women who used traditional methods to keep food and exercise diaries gained an average of 2.5 pounds, according to the study, which was published in the Journal of Medical Internet Research.

    “Text messaging has become popular and may be an effective method to simplify tracking of diet and exercise behavior,” Dori Steinberg, who was responsible for this research, said.

    Steinberg said, “Text messaging offers several advantages compared to other self-monitoring methods. Unlike web-based diet and exercise diaries, data in a text message can be entered quickly on nearly all cell phone platforms so it is very convenient to receive feedback. Besides, because of the limited number of words used in text messages, it saves time.”