If the ratio of a child's weight to height exceeds the level of 80% of children in the region, they are called obese. According to survey results over the years, the number of obese children in Linjiang City has been steadily increasing for 15 years. If the above is true, which of the following must also be true? ['The number of non-obese children in Linjiang City has been increasing for 15 years.', "For 15 years, children's physical training in Linjiang has become increasingly inadequate.", 'The weight of every obese child in Linjiang City exceeds the average weight of children in the city.', 'Over the past 15 years, the number of children with underweight in Linjiang City has been declining.']