Sharing economy: refers to the economic activities of individuals, organizations or enterprises to revitalize idle resources by means of modern information exchange means. Through this activity, the supply side can obtain additional benefits, and the demand side can obtain products and services at a lower cost. Which of the following belongs to the sharing economy? ["The industry committee of a community has established a WeChat group of owners. If there are idle items in the owner's home, they can take photos and send them to the group for other families to choose according to their needs. The owners are very satisfied with this approach of the industry committee.", 'Every year in the graduation season, college students who are about to leave the campus will set up booths in various corners of the campus to sell daily necessities that are not intended to be taken away. Younger students and youngsters often find a lot of "babies" from them. ".', "A courier company pushes the user's needs to free courier through mobile phone software. The free courier chooses the nearest order and delivers large and small packages in a timely and accurate manner to customers. The company's delivery costs have dropped significantly.", 'Xiao Zhong has established a website dedicated to publishing technical problems from various manufacturers, soliciting solutions designed by netizens for compensation, and transferring them after technical processing. Although manufacturers have not saved research and development costs, they like this method very much.']