C2C refers to the business activities between consumers and consumers using information network technology as a means and commodity exchange as the center. According to the above definition, Which of the following activities are C2C:. ['A community points out the "used property replacement" service.', "University student Xiao Li auctioned his old laptop on the Internet for 2,000 yuan. I didn't expect to buy a home that was his classmate Xiao Fang.", 'Every graduation season, the flea market on the school square is extremely popular. The "sale" seniors and the "Taobao" students all take what they need and return with a full load.', "When Xiaomei went shopping, he found a trench coat in a brand's clothing store, and he wrote down the information on the clothes tag. When he returned, he bought one from the brand's official website, saving a lot of money."]