Some people say: Those who do not enjoy some kind of social service are like a large desert, those who enjoy this kind of social service are like an oasis in the large desert, the desert is always engulfing the oasis, and the only way to protect the oasis is Turn the desert into an oasis as soon as possible. This text explains:. ['Law of Large Numbers.', 'Desert effect.', 'Oasis effect.', 'The rule of elimination.']