What is the hottest topic at your school? In Hangzhou Yongjin Middle School, it's money. The school had an activity called "making a living" recently. About 800 Junior 1 and Junior 2 students were divided into 112 teams. They went out to make money by selling things. What did they choose to sell? Some sold newspapers; some chose bottled water; some sold environmentally friendly shopping bags and bamboo baskets. Huqi's team decided to sell educational books in front of the Children Activity Centre. They thought parents would like to buy books for their children. But unfortunately , they came across urban management officers . The officers asked them to leave. "We played hide-and-seek with the officers for the whole morning," said Hu. "Finally we gave up and moved to other place. Wang Yongyi and her team sold ice cream in a square. They didn't meet any officers. But few people were interested in what they were selling. The team then put up a board saying the money was to help the "Project Hope" for country kids. It worked. More people came to their stall. A foreigner even gave them 100 yuan. Meng Zhaoxiang and his team were luckier. They sold all their cakes in four hours, spending 39.5 yuan and getting back 80 yuan. "It was not easy to make the money," said Meng. "Some people just looked. Others just tasted but didn't buy. Now I know how hard it is for our parents to earn the money we need to lead happy lives." According to the passage, the students learn   _  .
it's impossible for them to make money it's necessary for school to hold more activities it's very important for them to make a living it's not easy for their parents to make money