According to the passage, which of the following statements is true（）
A: The Chinese people have to pay tips in western countries.
B: The westerners don' t have to pay high tips in their own country.
C: Barbers, hotel bellboys and all sorts of other people can earn a living if they are not tipped.
D: Tipping varies from place to place, generally in the area of 20% of your bill.