A new study said about 65 percent of the online payments  last year were done with mobile devices. Along with the rapid growth of the online to offline business, the mobile payment has been further changing people's everyday life. According to findings published by Alipay, the mobile payment is more  _  in China's underdeveloped areas. In Tibet, 83.3 percent of the online payments were done with mobile devices in 2015. The region was followed by Guizhou, Gansu, Shanxi and Qinghai. Nearly 80 percent of the mobile payments were done in these regions and provinces. Li Chao, a researcher from iResearch Consulting Group, said that the lack of traditional business was the main reason why people used mobile payment more often. Although people in developed areas in China used mobile payments less often, they spent much more money. The study showed that people in Shanghai spent more than 100,000 yuan(15,210dollars) on average through Alipay, becoming the top Alipay users in China in 2015. As more and more companies are entering the mobile payment field in China, such as mobile payments in convenience  stores and movie theatres, online payment is sure to develop much more quickly. In the near future smartphones may replace wallets. Which of the following can be put in   _  ?
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