题干

阅读下列短文,从各题所给的四个选项(A B C D)中,选出最佳选项。

B

    Do you shop online with websites like Taobao? The money you pay doesn't go directly to the seller. Instead, it goes through Alipay, which keeps your money for a while. After you receive your goods and click the "confirm receipt" button, Alipay then gives the money to the seller.

    The process is called "third party online payment". There is a transfer station, or a third account, between sellers and buyers to make online shopping safe. Buyers don't need to worry about paying for goods and then receiving nothing. Sellers also get rid of the risk of receiving no money after sending out goods.

    These transfer stations are usually set up by payment service companies such as Alipay, Tenpay and Yeepay. Among them, Alipay is the biggest in China. It has more than 270 million active users, according to Xinhua.

    While most online sellers and shoppers like the third party online payment system, banks are not very happy. That is because companies like Alipay are fighting over money with the banks. Users can invest in financial products through Alipay and make money. Thus lots of people choose to put money in Alipay rather than in banks.

    But WeChat payment is not the same. WeChat doesn't have its own account. When paying through WeChat, the buyers' money goes directly to the sellers. That's why so many people are excited about receiving and handing out "red envelopes" or gift money to their friends on WeChat.

    Whether Alipay or WeChat payment, they are all trying to attract more users and make online shopping easier. These two companies are also promoting payments through fingerprints. New payment methods such as quick response codes have become popular too.

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同类题4

在学完氧气的性质后,某校课外小组同学对铁丝在氧气中燃烧的实验进行了更深入的探究.

说明:下述实验中所用的8根铁丝均从1根长铁丝上截取,并且长度相同.

探究1:铁丝燃烧是否需要纯氧?

实验内容:取5根铁丝,分别在体积分数为90%、70%、65%、60%、55%的氧气中进行实验.

实验记录如下:

V(O2)%

实验现象

90%

燃烧剧烈,燃烧时间长,实验成功

70%

燃烧比90%的弱,燃烧时间短,实验成功

65%

燃烧比70%的弱,燃烧时间比70%的短,实验成功

60%

燃烧比65%的弱,燃烧时间更短,实验成功

55%

难以燃烧,只是发红

探究2:铁丝绕成螺旋状的原因是什么?

关于铁丝绕成螺旋状的原因,甲同学认为是为了增大与氧气的接触面积,乙同学认为是聚热效果好,能使未燃的铁丝更好的预热.在老师的指导下,小组同学进行了实验,实验操作及现象如下表所示,实验中3个集气瓶均盛有等量的水和体积分数相同的氧气.

实验操作

实验现象

取3根铁丝,将1根拉直,另两根绕成宽窄不同的螺旋状,进行如图所示实验.

铁丝均燃烧,剧烈程度不同,II最剧烈,其次是 III,较弱的是 I.

回答下述问题:

(1)铁丝在氧气中燃烧的化学反应方程式为____ .

(2)通过探究1实验,丙同学得出结论:铁丝在氧气中燃烧,所需氧气的最低体积分数为60%,你对他得出的结论的看法是____ .

(3)探究2实验中,3根铁丝均要完全伸入集气瓶中的原因是____ 

(4)根据探究2实验,你认为____ (填“甲”或“乙”)同学说法合理,其理由是____ .

(5)探究1实验用排水法收集氧气时,每瓶都要留存30mL水,以防止熔融物炸裂瓶底.实验中收集体积分数为90%的氧气时,设应向空集气瓶中加入水的体积为x,请列出能求解x的计算式____ (空集气瓶容积为310mL,不考虑橡皮塞所占体积).