No. 1 SnapchatWith this app, the pictures people share with friends will disappear automatically(自动地) after they are seen. Snapchat has become more and more popular since 2012. Over 700 million photos have been shown daily by May 2014, up from 20 million per day in 2012.No. 2 UberThe on-demand car service app allows users to order a ride and get picked up within minutes. On-demand service means no need to reserve (预订) and no waiting in taxi queues. And the app can be used in more than 40 countries.No. 3 Whats AppWhatsApp became the world's most popular chat app in 2014 with over 600 million monthly users in August. It was also bought by Facebook in October for about $ 22 billion (about 136 billion yuan).No. 4 VenmoThe mobile payment service is used to share bills by friends, who get together to have dinner or do something else. It took Millennials' (生于1984-1995年间的"千禧一代") smart-phones by storm in 2014. It is said that among college students the word "Venmo" is now being used as a verb—"just Venmo me".(1)Which app can be chosen by those who like taking and sharing photos?